Chapter 11, Problem 22P

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8th Edition

Frederick J Gravetter + 1 other

ISBN: 9781133956570

Textbook Problem

The teacher from Problem 21 also tried a different approach to determining whether changing answers helps or hurts exam grades. In another class, students were told to review their final exams and change any answers and wanted to before turning them in. However, the students had to indicate both the original answer and the changed answer for each question. The teacher graded each exam twice, once using the set of original answers and once with the changes. In the class of *n* = 22 students, the exam scores improved by an average of *M _{D}* = 2.5 points with changed answers. The standard deviation for the difference scores was

To determine

The sufficiency of data to conclude that rethinking and changing answer significantly improve scores.

Explanation

**Given info:**

The mean difference

**Calculation:**

The estimate variance using sample variance is

*Null hypothesis:*

*Alternative hypothesis*

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