Asia-Pacific Forum on Science Learning and Teaching, Volume 11, Issue 2, Article 1 (Dec., 2010) Didem INEL and Ali Günay BALIM The effects of using problem-based learning in science and technology teaching upon students’ academic achievement and levels of structuring concepts Previous Contents Next

Results and Interpretation

This part of the study investigates the effects of using problem-based learning in teaching science and discusses the data obtained for each sub-problem before and after the experimental application.  The results of the data interpretation analysis is also reported.

Results and Interpretation concerning the First Sub-problem

The first sub-problem of the study was: “Is there a significant difference between the posttest academic achievement scores of the students in the experiment group taught by the problem-based learning method and the students in the control groups taught only on the basis of the science and technology curriculum?” In order to resolve the problem, the pretest and posttest academic achievement scores of the students in the experimental and control groups were compared using the Mann Whitney U test, a non-parametric statistical technique.

Table 2. Results of the Mann Whitney U Test to Compare the Groups’ Pretest Academic Achievement Scores

GROUPS	N	Rank Average	Sum of Ranks	U	Z	p
EXPERIMENTAL GROUP	20	20.53	410.50	200.50	0.253	.801*
CONTROL GROUP	21	21.45	450.50

* The difference is insignificant since p>.05.

An examination of the findings in Table 2 reveals the results of Mann Whitney U test for the pretest academic achievement scores of the students in the experimental and control groups did not show any statistical difference (Z=0.253; p=.801>.05). The rank average of the pretest scores of the experimental group students was 20.53, while the students in the control group had a pretest score rank average of 21.45. The close rank averages of the groups’ pretest academic achievement scores indicate that before the experimental application, the experimental and control groups had somewhat equal pretest academic achievement levels.

Table 3. Results of the Mann Whitney U Test to Compare the Groups’ Posttest Academic Achievement Scores

GROUPS	N	Rank Average	Sum of Ranks	U	Z	p
EXPERIMENTAL GROUP	20	25.55	511.00	119.00	2.382	.017*
CONTROL GROUP	21	16.67	350.00

* The difference is significant since p<.05.

An examination of the findings in Table 3 shows that the results of the Mann Whitney U test applied to the posttest academic achievement scores of the students in the experimental and control groups revealed a statistically significant difference at the level of p<.05 (Z=2.382; p=.017<.05). The rank average of the posttest scores of the experimental group students was 25.55, while the students in the control group had a posttest score rank average of 16.67. The analyses had shown no significant difference between the rank averages of the groups’ pretest academic achievement scores; however, an examination of the rank averages of their posttest academic achievement scores demonstrates that the students in the experimental group had higher academic achievement than those in the control group.This result indicates that the experimental group students attained higher success after the experimental application when compared to their peers in the control group.

Table 4. Results of the Wilcoxon Signed-Ranks Test to Compare the Pretest-Posttest Academic Achievement Scores of the Students in the Experimental Group

Academic Achievement Posttest-Pretest	N	Rank Average	Sum of Ranks	Z	p
Negative Rank	1	1.50	1.50	3.873	.000*
Positive Rank	19	10.97	208.50
Equal	0

* The difference is highly significant since p<.001.

As an examination of the findings in Table 4 shows there is a significant difference between the pretest and posttest academic achievement scores of the students in the experimental group (Z=3.873, p=.000<.001). The sum of their negative ranks for the experimental group students’ academic achievement scores was found to be 1.50, while their sum of positive ranks is 208.50. Given the sum of ranks for the difference scores, the observed difference is in favor of positive ranks, or in other words, the posttest scores of the experimental group. On the basis of the results obtained, it could be argued that the use of the problem-based learning method in the science and technology curriculum significantly increased the academic achievement levels of the experimental group students.

Table 5. Results of the Wilcoxon Signed-Ranks Test to Compare the Pretest-Posttest Academic Achievement Scores of the Students in the Control Group

Academic Achievement Posttest-Pretest	N	Rank Average	Sum of Ranks	Z	p
Negative Rank	2	1.50	3.00	3.709	.000*
Positive Rank	17	11.00	187.00
Equal	2	-	-

* The difference is highly significant since p<.001.

As will be revealed by an examination of the findings in Table 5, there is a significant difference between the pretest and posttest academic achievement scores of the students in the control group (Z=3.709, p=.000<.001). The sum of the negative ranks for the control group students’ academic achievement scores was found to be 3.00, while their sum of positive ranks is 187.00. Given the sum of ranks for the difference scores as a result of the analyses, the observed difference is in favor of positive ranks, or in other words, the posttest scores of the control group. On the basis of the results obtained, it could be argued that the science and technology curriculum significantly increased the academic achievement levels of the control group students.

Results and Interpretation concerning the Second Sub-problem

The second sub-problem of the study was formulated as follows: “Is there a significant difference between the posttest ‘construction levels of the concepts regarding the subject’ of the students in the experimental group taught by the problem-based learning method and the students in the control groups taught only by the science and technology curriculum?” In order to resolve the problem, the pretest and posttest concept construction levels of the students in the experimental and control groups were compared using Mann Whitney U test, a non-parametric statistical technique.

Table 6. Results of the Mann Whitney U Test on the Pretest Concept Construction Levels of the Students in the Experimental and Control Groups

GROUPS	N	Rank Average	Sum of Ranks	U	Z	p
EXPERIMENTAL GROUP	20	22.18	443.50	186.50	0.614	.539*
CONTROL GROUP	21	19.88	417.50

* The difference is insignificant since p>.05.

An examination of the findings in Table 6 reveals that the results of Mann Whitney U test, applied to compare the pretest average scores for concept construction levels of the students in the experimental and control groups, did not show any statistical difference (Z=0.614, p=.539>.05). The rank average of the pretest scores of the experimental group students was 22.18, while the students in the control group had a pretest score rank average of 19.88. The close rank averages of the groups’ pretest scores for concept construction levels indicate that before the experimental application, the experimental and control groups had somewhat equal construction levels of the concepts regarding the subject.

Table 7. Results of the Mann Whitney U Test on the Posttest Concept Construction Levels of the Students in the Experimental and Control Groups

GROUPS	N	Rank Average	Sum of Ranks	U	Z	p
EXPERIMENTAL GROUP	20	26.63	532.50	97.50	2.935	.003*
CONTROL GROUP	21	15.64	328.50

* The difference is highly significant since p<.01.

An examination of the findings in Table 7 shows that the results of Mann Whitney U test, applied to compare the posttest average scores for concept construction levels of the students in the experimental and control groups, revealed a statistically significant difference (Z=2.935, p=.003<.05). The rank average of the posttest scores of the experimental group students was 26.63, while the students in the control group had a posttest score rank average of 15.64. As a result, there was no significant difference between the groups’ concept construction levels before the experimental application; however, an examination of the rank average of their posttest scores for concept construction levels demonstrates that the students in the experimental group had higher concept construction levels than those in the control group.

Table 8. Results of the Wilcoxon Signed-Ranks Test on the Pretest-Posttest Concept Construction Levels of the Students in the Experimental Group

Concept Construction Posttest-Pretest	N	Rank Average	Sum of Ranks	Z	p
Negative Rank	1	1.00	1.00	3.883	.000*
Positive Rank	19	11.00	209.00
Equal	0

* The difference is highly significant since p<.001.

As revealed by the results in Table 8, there is a significant difference between the pretest and posttest scores of concept construction levels for the students in the experimental group (Z=3,883, p=.000<.001). For these experimental group students, the negative sum of ranks of the scores of concept construction levels was found to be 1.00, while the positive sum of ranks of their scores was 209.00. Given the sum of ranks for the difference scores, the observed difference is in favor of positive ranks, or in other words, the posttest scores of the experimental group. On the basis of the results obtained in the analyses, it could be argued that the use of the problem-based learning method in the science and technology curriculum significantly enhanced the concept construction levels of the experimental group students.

Table 9. Results of the Wilcoxon Signed-Ranks Test on the Pretest-Posttest Concept Construction Levels of the Students in the Control Group

Concept Construction Posttest-Pretest	N	Rank Average	Sum of Ranks	Z	p
Negative Rank	3	2.67	8.00	3.737	.000*
Positive Rank	18	12.39	223.00
Equal	0

* The difference is highly significant since p<.001.

As shown by the results in Table 9, there is a significant difference between the pretest and posttest scores of concept construction levels for the students in the control group at the level of p<.001  (Z=3.737; p=.000<.001). For the control group students, the negative sum of ranks of the scores of concept construction levels was found to be 8.00, while the positive sum of ranks of their scores was 223.00. Given the sum of ranks for the difference scores, the observed difference is in favor of positive ranks, or in other words, the posttest scores of the control group. These results suggest that the science and technology curriculum significantly enhanced the concept construction levels of the control group students.