Physics learning by PhET simulation-assisted using problem based learning (PBL) model to improve students' critical thinking skills in work and energy chapters in MAN 3 Sleman

The results of the analysis of the instrument in the form of learning devices PhET simulations-assisted using PBL model

After we know together about what data is sought in this study by using instruments that researchers have developed, then we first need to know about the feasibility of research instruments in the form of learning devices PhET simulations-assisted using PBL models that researchers have developed. The feasibility data of this research instrument is in the form of data on the validity and reliability of the instruments that have been provided by expert and practitioner validators, and have been analyzed using equations 1 and 2. The first analysis of the research instrument was to analyze the feasibility (validity and reliability) of the learning devices PhET simulation-assisted using problem based learning (PBL) model. Meanwhile, the results of the analysis of the validity of learning devices PhET simulation-assisted using PBL model can be shown in Table 3 below.

Table 3. Validation results of learning devices PhET simulation-assisted using PBL model

No.	Assessment Item	Validity (V)	Category
RPP PBL Based on PhET Simulation
A.	Subject Identity	0.92	Very Good
B.	Formulation of Indicators	0.80	Very Good
C.	Formulation of Learning Objectives	0.79	Good
D.	Selection of Teaching Materials	0.86	Very Good
E.	Selection of Learning Resources	0.80	Very Good
F.	Selection of Learning Medium	0.83	Very Good
G.	Learning Model	0.92	Very Good
H.	Learning Scenarios	0.79	Good
I.	Assessment	0.79	Good
	Validity of RPP PBL Based on PhET Simulation	0.82	Very Good
PhET Simulation
A.	Learning	0.78	Good
B.	Curriculum	0.75	Good
C.	Materials Content	0.78	Good
D.	Coloring	0.79	Good
E.	Word and Language Spelling	0.78	Good
F.	Display on Screen	0.89	Very Good
G.	Instructions	0.92	Very Good
	Validity of PhET Simulation	0.81	Very Good
LKPD PBL Based on PhET Simulation
A.	The Didactic Aspect	0.79	Good
B.	The Quality Aspects of Material in LKPD	0.80	Very Good
C.	The Aspects of Compliance LKPD PBL Based on PhET Simulation	0.83	Very Good
	Validity of LKPD PBL Based on PhET Simulation	0.80	Very Good
Critical Thinking Test
A.	The Aspects of Learning Guides	0.83	Good
B.	The Quality Aspects of Matter in Test	0.78	Good
C.	The Aspects of Pictures and Language	0.87	Very Good
D.	The Aspects of Conformity of Critical Thinking Test	0.79	Good
	Validity of Critical Thinking Skills Test	0.83	Very Good
	Validity of learning devices PhET simulation-assisted using PBL model	0.82	Very Good

Based on the results of the validation of the instruments used in this study which can be shown in Table 3, the results of the validity of learning devices PhET simulation-assisted using PBL models of 0.82 with very good categories. With the details, the results of the validity of the LKPD PBL based on PhET simulation are 0.82 with a very good category, the results of the validity of the learning media in the form of PhET simulations are 0.81 which are included in the very good category, the results of the LKPD PBL validity based on the PhET simulation are equal to 0.80 which is included in the excellent category, and the results of the validity of the critical thinking skills test that is equal to 0.83 which is included in the excellent category. Therefore, it can be stated that the learning devices PhET simulation-assisted using PBL models consisting of RPP PBL based on PhET simulation, PhET simulation, LKPD PBL based on PhET simulations, and critical thinking skills tests are valid and suitable for use in physics learning class X MIPA in MAN 3 Sleman consisting of modeling class and implementation class.

The learning device can be declared appropriate in accordance with the results of the validity provided by expert and practitioner validators, so that the learning device can be used in all class X MIPA whose characteristics of students and other characteristics are similar to the characteristics of class X MIPA students in MAN 3 Sleman. This is consistent with the view of Hasibuan et al.. (2018) which states that a learning device that is developed and meets the established eligibility standards, then the learning device can be used in physics-specific learning activities in all high schools with homogeneous characteristics and possible learning objectives can be achieved well. However, the results of the validity of the learning devices developed by researchers in this study were not in the highest validity scores in the excellent category. However, the validity score of this learning device is close to the lowest score in the excellent category. This is a lot of factors that influence it, can be influenced by the number of validators that are less numerous and also the valuation of validiators that tend to be random which assesses in the lowest to highest assessment range. The results of a random assessment by the validiator from the lowest to highest assessment range are characteristic of a learning instrument or device that is valid or feasible to be used in research (Huang & Chiu, 2015).

After the instruments used in this study were analyzed for validity using the Aiken's V equation, the next step was to analyze the other parts of the feasibility, i.e analyzing the reliability of the research instrument or the reliability of PBL learning devices assisted with PhET simulations. In other words, the results of the reliability are also used as part of the feasibility of the PBL learning device assisted by PhET simulations that have been developed by researchers. The results of the PBL learning device assisted by the PhET simulation for energy sub-subjects in the modeling class and implementation class can be presented in Table 4 below.

Table 4. Reliability of learning devices PhET simulation-assisted using PBL model

Reliability of LKPD PBL Based on PhET Simulation
Item number of LKPD PBL Based on PhET Simulation	Modeling Class		Implementation Class
Item number of LKPD PBL Based on PhET Simulation	Average of PA per Item (%)	Category	Average of PA per Item (%)	Category
1.	95.14	Reliable	93.93	Reliable
2.	95.98	Reliable	93.86	Reliable
3.	97.20	Reliable	95.59	Reliable
4.	94.46	Reliable	94.46	Reliable
5.	97.22	Reliable	93.44	Reliable
6.	94.11	Reliable	96.28	Reliable
7.	98.01	Reliable	94.72	Reliable
Quantity	96.27	Reliable	95.31	Reliable
Reliability of Pretest on Critical Thinking Skills
Item number of Pretest on Critical Thinking Skills	Modeling Class		Implementation Class
Item number of Pretest on Critical Thinking Skills	Average of PA per Item (%)	Category	Average of PA per Item (%)	Category
1.	91.64	Reliable	91.33	Reliable
2.	94.87	Reliable	96.32	Reliable
3.	98.17	Reliable	98.65	Reliable
4.	96.61	Reliable	97.75	Reliable
5.	97.52	Reliable	96.21	Reliable
Quantity	96.54	Reliable	95.62	Reliable
Reliability of Posttest on Critical Thinking Skills
Item number of Posttest on Critical Thinking Skills	Modeling Class		Implementation Class
Item number of Posttest on Critical Thinking Skills	Average of PA per Item (%)	Category	Average of PA per Item (%)	Category
1.	95.63	Reliable	93.67	Reliable
2.	95.51	Reliable	94.69	Reliable
3.	97.44	Reliable	97.49	Reliable
4.	97.09	Reliable	97.75	Reliable
5.	96.67	Reliable	94.85	Reliable
Quantity	97.18	Reliable	96.26	Reliable
Reliability of learning devices PhET simulation-assisted using PBL model	96.66	Reliable	95.73	Reliable
	96.20		Reliable

Based on Table 4, we can observe that in general PBL learning device assisted by PhET simulations that have been developed by researchers composed of LKPD PBL and critical thinking skills test questions are reliable with a percentage of reliability of 96.205. Meanwhile, in detail, we can see empirical data on the level of reliability of LKPD PBL assisted by PhET simulation for the modeling class obtained a reliability percentage of 96.27% and 95.31% for the implementation class. The percentage of reliability for the pretest of critical thinking skills in the modeling class was 96.54% and 95.62% for the implementation class. Meanwhile, the percentage of reliability for pretesting critical thinking skills in the modeling class was 97.18% and 96.26%. The details of the data are all categorized as reliable because they meet the reliability requirements of the percentage of agreement (PA) value, where the research instrument in this case the PBL learning device assisted by the PhET simulation can be said to be reliable, if the percentage of agreement (PA) value obtained for each research instrument more than 75% (Borich, 1994).

Based on Table 4, we can observe that the results of the reliability of learning devices for the modeling class and implementation class in MAN 3 Sleman obtained different reliability results. In this case the level of reliability of PBL learning device with the assisted of PhET simulations for modeling class obtained higher reliability results than the reliability of the implementation class. Nevertheless, the reliability of PBL learning devices assisted by PhET simulations in both classes is at 90% intervals and all are included in the reliable category. This can happen, one of which is influenced by the assessors who provide the lowest and highest scores of diverse or many assessors. In addition, it can also be caused by the achievement of work on LKPD PBL assisted by PhET simulation and the results of critical thinking skills tests in the implementation class are lower than in the modeling class, so the percentage of reliability is also higher for the modeling class. This often happens because each assessor gives an assessment of each research instrument that has different views, there are times when the first rater gives the highest score on a particular item number, but the other rater gives the lowest score on that item number (Yuliani & Saragih, 2015). Therefore, the percentage acquisition of reliability of each research instrument in the modeling class and the implementation class is also different, but still in the same interval.

The results of data analysis class X MIPA (modeling class and implementation class) at MAN 3 Sleman

In this data analysis section, we first discuss the physics learning activities of class X MIPA conducted by physics teachers at MAN 3 Sleman. Class X MIPA physics learning activities in MAN 3 Sleman are quite dense and the year-end assessment (PAT) implementation schedule is advanced, so teachers need to accelerate the explanation of all physics chapter in class X MIPA. Nevertheless, many students do not understand the physics chapter provided by the teacher with an explanation that is faster than usual. Finally, the solution of the physics class X MIPA teacher at MAN 3 Sleman is to explain the impulse and momentum chapter to students and the work and energy chapter with the energy sub-topic explained by the modeler or researcher in class X MIPA 1 for 2 hours or 90 minutes. Keep in mind the class X MIPA 1 at MAN 3 Sleman is used as a modeling class, which means that the class is stimulated with PBL learning tools assisted by PhET simulations and researchers are tasked with explaining work and energy chapter to students. Meanwhile, the solution made by the physics teacher in class X MIPA MAN 3 Sleman is to explain the chapter momentum and impulses to students first and the work and energy chapter with energy sub-points explained by the teacher in class X MIPA 3 for 2 hours or 90 minutes. Keep in mind class X MIPA 1 at MAN 3 Sleman is used as a modeling class, which means class stimulated with PBL learning tools assisted by PhET simulations and physics teachers are tasked with explaining work and energy chapter to students.

Like the research conducted by Savery (2015) which states that research activities in physics learning conducted by different instructors, both different in terms of delivering physics chapter to students or different in terms of the frequency of instructors' habit of delivering physics chapter to students will be able to detect or measuring students' understanding of physics concepts and being able to measure their level of adaptation and also their confidence in new and different situations. In addition, the implementation of physics learning with different instructors combined with PBL models will be very obvious in measuring their critical thinking skills, this is because the two different instructors will certainly provide a basic understanding and apperception of different physical materials (Jonassen & Hung, 2015).

Meanwhile, the results of the implementation of research in two MIPA class at MAN 3 Sleman conducted by researchers/modelers and physics teachers are as follows. In carrying out research activities in slass X MIPA 1 in MAN 3 Sleman, which is used as a modeling class, there are some constraints in terms of the time allocation that has been planned in the lesson plan, but at the time the implementation was not according to the plan. The time allocation in the lesson plan (RPP) has been designed for 2 x 45 minutes, but the implementation of physics learning activities in class X MIPA 1 in MAN 3 Sleman as a modeling class held on Monday at 07.00 WIB until 08.30 WIB is not full 2 x 45 minutes because in the first 15 minutes used by students to read the holy book of the Qur'an. Meanwhile, the time allocation given by physics teacher class X MAN 3 Sleman for learning activities and posttest in modeling class was only on Monday, April 23, 2016 for 2 hours of learning, but the implementation was not full 2 x 45 minutes because in the first 15 minutes used by students to read the Qur’an.

Therefore, the time spent on learning physics and posttest activities in the modeling class is 75 minutes. For 45 minutes it is used for physics learning activities in the form of an explanation of skate board video games that are in accordance with the work and energy chapter, then students are guided by researchers/modelers to work on PBL LKPD using PhET simulation assistance. Meanwhile, the next 30 minutes are used to complete the posttest of critical thinking skills in the energy sub-topic. Learning activities in modeling class that experience a shortage of time that is not in accordance with the plans that have been prepared in the lesson plan. In the RPP that has been developed, the allotment of time for the implementation of learning activities in class X MIPA 1 in MAN 3 Sleman is 90 minutes, that time is used to explain learning videos to students, work on LKPD PBL, and also communicate each group about the results of the discussion they are in solving the physics problems given by the teacher and also the physical problems contained in the LKPD PBL assisted by the PhET simulation. Meanwhile, the plan to fill in the posttest critical thinking skills of students of class X MIPA 1 was not done right then after the learning activities were finished, but carried out at the next meeting before the explanation of the next chapter.

Meanwhile, research activities in the implementation class conducted by physics teacher class X MIPA 3 at MAN 3 Sleman experienced problems in presenting a PhET simulation by students. There are some groups of students who cannot use PhET simulations that have been shared by modelers on their cellphones or smartphones. This happens because the PhET simulation requires the Flash Player plugin on students' smartphones. If the student smartphone does not support Flash Player, the student smartphone cannot be used to operate the PhET simulation. So, the step taken by the teacher to overcome this problem is to ask the assisted of the modeler who was observing the course of learning by the teacher by lending a smartphone and laptop modeler to be used by students in operating the PhET simulation. This problem is in accordance with the statement Namgyel and Buaraphan (2017) which states that the PhET simulation can be operated in an offline model or without an internet signal, but requires devices such as smartphones and laptops that support the Flash Player plugin.

The feasibility of this research instrument in the form of PBL physics learning device assisted with PhET simulations on work and energy chapter in addition to being analyzed from validity and reliability, also their feasibility was analyzed based on students' responses to this research instrument. Specifically, the research instruments that were responded by students in this study were research instruments in the form of LKPD PBL assisted by PhET simulation and PhET simulation itself. This is because the two instruments are part of PBL learning device assisted by PhET simulations that function as a stimulus or treatment given by the modelers/researchers in this study. In addition, LKPD PBL and PhET simulation are also learning media for researchers' innovations which are the main physics learning media and as a substitute for media that are often used by physics class X MIPA teachers in MAN 3 Sleman which tend not to be student-centered. Therefore, the results of students' responses to the use of LKPD PBL assisted by the PhET simulation and the PhET simulation itself can be shown in Table 5 below.

Table 5. The results of students' responses to LKPD PBL and PhET simulation

No.	Item number of LKPD PBL Based on PhET Simulation	Modeling Class		Implementation Class
No.	Item number of LKPD PBL Based on PhET Simulation	Validity of Each Aspect	Category	Validity of Each Aspect	Category
The students' responses to LKPD PBL assisted by PhET simulation
1.	Display Aspect	0.70	Very Good	0.76	Very Good
2.	Aspects of Language	0.68	Very Good	0.63	Very Good
3.	Aspects of Critical Thinking Skills	0.72	Very Good	0.69	Very Good
	Quantity	0.70	Very Good	0.70	Very Good
The students' responses to simulation
1.	Quality Content Aspects	0.77	Very Good	0.77	Very Good
2.	Aspect of Pleasure	0.73	Very Good	0.82	Very Good
3.	Aspects of Language	0.69	Very Good	0.75	Very Good
4.	Aspects of Learning Independencer	0.71	Very Good	0.73	Very Good
5.	Aspects of Use Illustration	0.78	Very Good	0.81	Very Good
	Quantity	0.74	Very Good	0.78	Very Good
The students' responses to LKPD PBL assisted by PhET simulation and PhET simulation		0.72	Very Good	0.74	Very Good
		0.73		Very Good

Based on Table 5, in general the response of modeling and implementation class students at MAN 3 Sleman in physics learning activities using LKPD PBL assisted by PhET simulation and PhET simulation itself received very good responses with a score of 0.73. The details are the results of modeling class students' responses in physics learning activities using LKPD PBL assisted by PhET simulations obtained a very good response with a score of 0.70 and also obtained an excellent response in the implementation class with a score of 0.70. Meanwhile, the results of modeling class students' responses in physics learning activities using PhET simulations obtained a very good response with a score of 0.74 and also obtained an excellent response in the implementation class with a score of 0.78. Therefore, the results of modeling class students' responses in physics learning activities using LKPD PBL assisted by PhET simulation and PhET simulation itself obtained a very good response with a score of 0.72 and also obtained an excellent response in the implementation class with a score of 0.74.

Based on these results we can discuss that physics learning devices with PBL models that are assisted by PhET simulations developed by researchers get very good responses from students. That is because the learning media especially the PhET simulation has never been used by students in physics learning activities before. In addition, students can already compare various kinds of learning media that they often use, and PhET simulations that are more interesting, interactive, and easier to assist understand physics than other physics enhancing media that are often used by their physics teachers (Eichler & Peeples, 2016). Therefore, based on the results of the validity, reliability, and student responses to the physics learning device using the PBL model assisted by the PhET simulation, in general the learning device developed by the researcher is suitable for use in the physics learning activities of work chapters and energy in class X MIPA both at MAN 3 Sleman or at any high school whereever the characteristics of the students are similar to the characteristics of the class X MIPA students at MAN 3 Sleman.

After we find out the situation in the modeling class and the implementation class during the research activities, then we next discuss the results that have been obtained from the two classes of X MIPA in MAN 3 Sleman. The results that we discussed first are the results of LKPD PBL assisted PhET in the modeling class and the implementation class. After explaining the work and energy chapter through learning videos about skate board games to students in class X MIPA 1, students are asked by modelers/researchers to solve the problems contained in the LKPD PBL using the assisted of a PhET simulation that has been installed on a laptop or android smartphone. In addition, in class X MIPA 3 or implementation class, the teacher also explained the work and energy chapter through learning videos about skate board games to students. After that, students of class X MIPA 3 were also asked by their physics teacher to solve the problems contained in the LKPD PBL by using the assisted of a PhET simulation that was installed on an Android laptop or smartphone. The stimulus given by modelers/researchers and physics subject teachers in class X MIPA to students is to provide problems regarding skate board games that include learning videos and PhET simulations. It aims so that students better understand work and energy chapter. Meanwhile, the results of LKPD PBL work based on PhET simulations conducted by students of class X MIPA 1 as a modeling class and students of class X MIPA 3 as implementation class can be shown in Table 6 below.

Table 6. Results of working of LKPD PBL based on PhET simulation

Modeling Class					Implementation Class
Score	Score Each Aspect in LKPD PBL			Total Score LKPD PBL	Score Each Aspect in LKPD PBL			Total Score LKPD PBL
Score	1st PBL Aspect	2nd PBL Aspect	3rd PBL Aspect	Total Score LKPD PBL	1st PBL Aspect	2nd PBL Aspect	3rd PBL Aspect	Total Score LKPD PBL
Quantity	128.00	164.40	264.00	1214.00	138.00	173.20	360.00	1364.00
Average	4.00	5.14	8.25	37.94	4.60	5.77	12.00	45.47
Minimal Score	0.00	1.40	0.00	19.00	3.00	3.60	12.00	41.00
Maximal Score	5.00	8.20	12.00	48.00	5.00	7.80	12.00	51.00
Achievement (%)	80.00	61.66	68.75	64.30	92.00	67.69	100.00	77.06
Category	Good	Bad	Bad	Bad	Very Good	Bad	Very Good	Quiet Good

Based on Table 6, for the modeling class and implementation class where PBL's 1st aspect of LKPD PBL is assisted by a PhET simulation that shows a syntax explanation about organizing students to learn, the 2nd aspect of PBL shows a syntax explanation of the development and presentation of the work/results of completion problems by students, and the third aspect of PBL shows the syntax about analyzing and evaluating the problem solving process that students do in groups. Based on the data in Table 8, it is easier for students in the modeling class and the implementation class to complete the items in the LKPD PBL based on the PhET simulation related to the 1st PBL syntax, which is about organizing students to learn. Meanwhile, students in both classes have difficulty in solving physics problems in LKPD PBL; assisted by PhET simulation related to the second PBL syntax, which is about developing and presenting their work/problem solving results. Meanwhile, student achievement in LKPD PBL assisted by PhET simulation is related to the 1st PBL syntax, which is about organizing students to learn reaching up to 80% for modeling class and 92% for implementation class. Student achievement in completing LKPD PBL assisted by PhET simulation is related to the second syntax, which is about developing and presenting work results or problem solving results obtained up to 61.66% and 67.695 for class implementation. Meanwhile, students' achievement in completing LKPD PBL was assisted by PhET simulation related to the 3rd syntax, which is about the analysis and evaluation of problem solving processes, reaching up to 68.75% and 100% for class implementation.

Based on these results, it can be discussed that in general, the two classes of X MIPA in MAN 3 Sleman, i.e the modeling class and the implementation class, have achieved almost the same aspects of PBL, i.e both classes are still weak in implementing the second aspects of the PBL model, i.e on the development and presentation of the results of problem solving. In addition, students in both of the class X MIPA are already good at organizing themselves to study physics. In general, students in class X MIPA are already proficient in organizing themselves to study physics, one of which is because these students do not experience significant difficulties in understanding apperception about problems in life about work and energy chapter provided by their modelers and teachers. This is very reasonable because the physics problems presented to students in the introduction to learning are simple problems and often involve students in the occurrence of these problems (Ernst et al.., 2017). In addition, the level of cognitive development of middle school students also supports the achievement of good results in the PBL aspect 1, because the level of cognitive development of middle school students is still classified as thinking towards the abstract (Karatas & Baki, 2017). However, students in the second class X MIPA began to experience obstacles when analyzing and developing solutions to more complex physics problems about work and energy chapter and they had never solved the problem before. This can happen because middle school students are also not accustomed to solving complex problems or a combination of various physical problems in a systematic and planned manner (Bachtiar, 2018). Meanwhile, the results of the subsequent data analysis are about the results of the students' pretest and posttest critical thinking skills in the modeling class and the implementation class, which are carried out before and after they study work and energy chapter with a PhET simulation. The results of the pretest and posttest critical thinking skills of students in the modeling class and the implementation class in MAN 3 Sleman can be observed in the following Figure 10.

Figure 10. Results of pretest and posttest achievement of critical thinking skills, i.e in the (a) modelling class, and (b) implementation class

Based on Figure 10, which shows the results of pretest and posttest critical thinking skills of students in the modeling class and the implementation class shows that the level of critical thinking skills in the initial conditions in the modeling class is 35.97% which is included in the very bad category. However, the level of critical thinking skills of students in the initial conditions in the implementation class was 35.43% which was included in the less good category. However, after students study the work and energy chapters using the assisted of the PhET simulation and solve the problems regarding the work and energy chapters in the LKPD PBL assisted by the PhET simulation, the student learning outcomes achieved in the modeling class by 64.30% which are included in the less good category. In addition, the achievement of student learning outcomes in the implementation class after learning work and energy chapters with the assisted of PhET simulations and solving problems regarding work and energy chapters on LKPD PBL assisted by PhET simulations, the achievement of learning outcomes of 77.06% which is included in the quite good category.

However, the results of students 'critical thinking skills shown in the diagram in Figure 10 show that the results of students' critical thinking skills in the modeling class amounted to 59.81% which were included in the very poor category. The increase in critical thinking skills is indicated by the standard gain of 0.35 which is included in the medium category. Meanwhile, the results of students' critical thinking skills in the implementation class were 77.36% which were included in the quite good category. The increase in critical thinking skills as indicated by the standard gain value of 0.61 is included in the medium category.

Based on these results, students in the modeling class find it easier in the aspects of critical thinking skills about combining with an increase of 30.99% from the pretest and posttest results for the energy sub-topic. The results also apply to students in the implementation class, where students are easier in the aspects of critical thinking skills about combining with an increase of 43.62% of the results of the pretest and posttest for the energy sub-topic as well. This is caused by the cognitive development characteristics of middle school students who are at the formal operational stage who have many creative, innovative, and critical ideas (Asyari et al.., 2016). Therefore, it is easier for them to combine different things in the energy sub-topic well, because the cognitive level of students the class X MIPA in MAN 3 Sleman is more supportive of critical thinking skills on combining aspects than other aspects. However, students still find it difficult to analyze the problems in life about the work and energy chapters raised in the LKPD PBL with the assisted of a PhET simulation. In addition, these results also indicate some errors that occur during physics learning activities, one of which teachers still rarely provide variations in physics practice questions in addition to the calculation and tendency of physics learning is only centered on the teacher (Fuad et al., 2017).

In general, students' critical thinking skills in modeling and implementation class have increased although not too large after they have learned the work and energy chapters with the assisted of PhET simulations. However, the results of critical thinking skills in the modeling and implementation class are different. It is very many factors that influence it, i.e the explanation of the work and energy chapters performed by two different instructors (physics teacher class X MIPA in MAN 3 Sleman who is used to chatting with students and also with modelers/researchers for the first time chatting with students of class X MIPA in MAN 3 Sleman). Another factor is the seriousness of students in paying attention to the explanation of the work and energy chapters explained by the two instructors. This is still a problem among high schools in Indonesia, where students tend to be indifferent or not care about the researchers who are researching them (Apino & Retnawati, 2017).

Most students often question whether what is done by researchers influences their final physics score or not, basically the high school students in Indonesia are still fixated on the value of the learning outcomes they get, not on the knowledge or competencies they have gained while participating in physics learning activities in class (Kong, 2015). In addition, the results of improving critical thinking skills in the modeling class and implementation class in MAN 3 Sleman which are still relatively low are also in accordance with PISA data on the ranking of high-level thinking skills especially critical thinking skills of high school students in Indonesia which are still low (Tanujaya et al.., 2017). However, with the innovation in physics learning activities at MAN 3 Sleman using the assisted of the PhET simulation, students of class X MIPA become more enthusiastic and more challenged in studying other physics materials in detail. That is because the PhET simulation is a learning medium that is easy to operate and can be used at any time while having a smartphone, PC, or laptop (Widyastuti et al., 2019).

Furthermore, the next discussion is about the effectiveness of the use of PhET simulations in the physics learning work and energy chapters in the modeling class and implementation class in MAN 3 Sleman. As was previously known that to analyze the effectiveness of the use of this PhET simulation, we analyzed it using the one sample t-test technique with the assisted of the analysis program that is using the SPSS 21 program. Decision criteria used are Ho rejected if the value of sig. obtained through the SPSS program is less than the level of significance (α) (Liu & Yao, 2016). The reference used in the effectiveness test of the PhET simulation is 75, which is the minimum limitation criteria score (KKM) that must be achieved by students after attending physics learning using a PhET simulation in the work and energy chapter. The value of 75 becomes a reference to determine the effectiveness of the PhET simulation applied in physics learning activities in terms of improving students' critical thinking skills.

Meanwhile, the hypothesis used for the one sample t-test for the effectiveness of the use of PhET simulation in the modeling class and the implementation class at MAN 3 Sleman in terms of improving students' critical thinking skills is as follows. For modeling class, Ho: PhET simulations are not effective in terms of improving students' critical thinking skills in the modeling class and Ha: PhET simulations are effective in terms of improving students' critical thinking skills in modeling class. For implementation class, Ho: PhET simulations are not effective in terms of improving students' critical thinking skills in classroom implementation and Ha: PhET simulations are effective in terms of improving students' critical thinking skills in classroom implementation. Mathematically, the two hypotheses for the modeling class and the implementation class can be written as follows, Ho: μ≤75 and Ha: μ>75. The results of one sample t-test on the effectiveness of using PhET simulations in the work and energy chapters in the modeling class and implementation class in MAN 3 Sleman can be shown in the following Table 7.

Table 7. Results of one sample t-test analysis

Class	Test Value = 75
	T	df	Sig. (2-tailed)	Mean Difference	95% Confidence Interval of the Difference
					Lower	Upper
Modeling Implementation	-15.370	31	.000	-29.5487	-33.4696	-25.6279
	-8.1	29	.000	-20.13	-25.228	-15.03

Based on Table 7, we can observe that the PhET simulation in the modeling class and implementation class in MAN 3 Sleman is effectively used to improve students' critical thinking skills in the physics learning activities of work and energy chapters. PhET simulation is effectively used in physics learning activities in the modeling class and implementation class in MAN 3 Sleman, due to the value of sig. (2-tailed) in Table 7 is obtained at 0.00 which amount is less than 0.05. Therefore, Ha for modeling class and implementation class is accepted or PhET simulation is effective in terms of improving students' critical thinking skills in modeling class and implementation class. The effectiveness of the use of PhET simulation in learning physics is also in accordance with the views of Radnai et al.. (2019) which states that with the assisted of simulation media or games like PhET in learning science especially mathematics and physics, the learning activities or explanation of physics and mathematics material to physics is more effective than other media and student learning outcomes are also better. In addition, the effectiveness of the use of PhET simulations in physics learning work chapters and energy is also due to the nature of PhET simulations which are more interactive, communicative, and certainly more interesting for students in learning physics material (Correia et al., 2019). PhET simulation media is also one of the physics learning media that allows physics learning activities to be centered on students, so students can develop the concepts of physics they already know by solving critical physics problems with the assisted of the PhET simulation itself (Ekmekci & Gulacar, 2015).