An educator believes that new directed reading activities in the
classroom will help elementary school pupils improve some aspects
of their reading ability. She arranges for a third-grade class of
21 students to take part in these activities for an eight-week
period. A control classroom of 23 third-graders follows the same
curriculum without the activities. At the end of the eight weeks,
all students are given a Degree of Reading Power (DRP) test, which
measures the aspects of reading ability that the treatment is
designed to improve.
Group
n
x-bar
s
Treatment
21
51.48
11.01
Control
23
41.52
17.15
Using software, the degrees of freedom are 37.9 and the 95%
confidence interval for the true difference (treatment -
control) in average scores for the two groups is (1.2,
18.7)
A.
This confidence interval is evidence that the new directed
reading activities in the classroom improve the average DRP test
score.
B.
Based on this confidence interval, we can conclude the results
of a two tailed significance test for the difference between the
means would not be significant at the 0.05 level.
C.
This confidence interval is not evidence that the new directed
reading activities in the classroom improve the average DRP test
score.
D.
It is not possible to draw any conclusions regarding average DRP
test scores from a confidence interval.