An educator believes that new directed reading activities in the classroom will

Question

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.

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)

This confidence interval is evidence that the new directed reading activities in the classroom improve the average DRP test score.

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.

This confidence interval is not evidence that the new directed reading activities in the classroom improve the average DRP test score.

It is not possible to draw any conclusions regarding average DRP test scores from a confidence interval.

Explanation / Answer

The correct option is Option A.

EXPLANATION

Since, the confidence interval does not contain zero, the effect of the treatment is statistically significant. Also, since the 95% confidence interval for (treatment-control) is strictly positive, it shows that the directed reading activity improves the average DRP test score of children. Thus, the confidence interval is an evidence that the new directed reading activities improve the average DRP test score.

Thus, clearly, option A is correct and option C and D are incorrect.

Option B is incorrect because it is clear from the confidence interval that the results of a two tailed significance test for difference between means would be significant at the 0.05 level because the conclusion (most of the times) is the same from the confidence interval and a hypothesis test.

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