PS296 Lecture Notes - Lecture 16: Pooled Variance, Standard Deviation, Confidence Interval
Independent samples t test full example:
A prof suspects that students do worse on multiple choice vs short answer tests. The following table
presents the scores for one group of students on a multiple choice test and another group of students on
a short answer test on the same topic. Did students score worse on the multiple choice test? Calculate
appropriate test, and 95% confidence interval and effect size.
-we know it is independent test bc there are two different groups, not two different variables
-one tailed test at alpha = .05 on the left side
Step 1:
H0: Test scores are the same for both groups. μ1 = μ2
HA: Test scores are lower on the multiple choice than the short answer test. μ1 < μ2 or μ1 – μ2 < 0
xbar1 = 4.167
xbar2 = 5.667
n1 = 6, n2 = 6, N = 12
Document Summary
A prof suspects that students do worse on multiple choice vs short answer tests. The following table presents the scores for one group of students on a multiple choice test and another group of students on a short answer test on the same topic. Calculate appropriate test, and 95% confidence interval and effect size. We know it is independent test bc there are two different groups, not two different variables. One tailed test at alpha = . 05 on the left side. H0: test scores are the same for both groups. Ha: test scores are lower on the multiple choice than the short answer test. 1 < 2 or 1 2 < 0 xbar1 = 4. 167 xbar2 = 5. 667 n1 = 6, n2 = 6, n = 12. Make sure x1 and x2 stay consistent with the way you"ve laid out your table.
