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Table 5.
Paired t-test comparisons of percentage improvement on pretests and posttests for students grouped by level of prior understanding, based on pretest scores (excludes students earning 100% on the pretest).
Groups (Pretest Percentage Earned)One
(≤50%)
Two
(51–79%)
Three
(80–99%)
Pretest percentage (X¯ ± SE) 44 ± 1 65 ± 1 84 ± 1 
Posttest percentage (X¯ ± SE) 71 ± 3 80 ± 2 92 ± 1 
n 51 113 108 
t 7.952 9.969 8.252 
p <0.001 <0.001 <0.001 
Cohen's d 1.114 0.938 0.794 
Groups (Pretest Percentage Earned)One
(≤50%)
Two
(51–79%)
Three
(80–99%)
Pretest percentage (X¯ ± SE) 44 ± 1 65 ± 1 84 ± 1 
Posttest percentage (X¯ ± SE) 71 ± 3 80 ± 2 92 ± 1 
n 51 113 108 
t 7.952 9.969 8.252 
p <0.001 <0.001 <0.001 
Cohen's d 1.114 0.938 0.794 
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