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Table 5. Result of Normality Test data value of critical thinking test 
Kolmogorov-Smirnov
a
 
Shapiro-Wilk 
Pretest-
posttest 
Statistic 
df 
Sig. 
Statistic 
df 
Sig. 
.067 
64 
.200
*
.985 
64 
.649 
The results of testing the normality of scores for the results of learning critical thinking get the results 
of Sig > 0.05 which mean that the data is normally distributed. Result of Paired Sample T-test of student 
critical thinking skills are presented in Table 6.
Table 6. Result of Paired Sample T-test of student critical thinking skills 
Variable 
Average score of 
pretest 
Average score of 
posttest 
Sig. 
pretest-posttest score 
29.5703 
70.3542 
0.000 
Parametric test results for paired data show Sig. 0.000. The criteria for drawing conclusions are if 
the significance level is (Sig.) <0.05. Paired Sample T-test results show that learning devices based on 
problem-based learning are effective to improve student’s critical thinking skills. 
3.6. Result of observation sheet 
Improvement of each critical thinking skills aspect are presented in Figure 5. 
 
Figure 5. Improvement of each critical thinking skills aspect
Each aspect of critical thinking skills has different improvement from the 1
st
meeting until the 4
th
meeting. Overall, these result shows that every aspect were improved. The ability of students in 

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The International Seminar on Bioscience and Biological Education
IOP Conf. Series: Journal of Physics: Conf. Series 1241 (2019) 012020
IOP Publishing
doi:10.1088/1742-6596/1241/1/012020
7
analyzing obtained through identification of problems so that they obtain concepts and descriptions and 
submit opinions through their learning experience [20]. The aspect of interpreting defined as the activity 
of classifying, understanding, and expressing meaning. This is indicated by the ability of students to 
summarize the description of the patterns of interrelationship between information. Students are able to 
analyze tables and explain them well. Active discussion can improve critical thinking skills such as 
problem identification, categorization, classification, and interpretation [21]. 
Critical thinking skills in evaluation aspect is defined as an activity to assess the credibility of a 
statement by describing one’s perception. The ability to evaluate were developed through discussion 
activities. Students can respond to each other’s statements, provide alternative answers, and evaluate 
information sources during discussions. This stage provides many opportunities for students to express 
their opinions and process the feedback regarding answers to questions. The response from the 
presentation results enables students to develop critical thinking skills in the evaluation aspect [22]. 
Inference aspects can be interpreted as activities to identify and select elements needed to form 
conclusions [22]. Facione states that student's interpretation skills can arise if they are challenged to 
work with data and faced with problems, so they will work by interpreting data and problems first, 
before finding concepts.