Essentials of Statistics for the B...

8th Edition
Frederick J Gravetter + 1 other
ISBN: 9781133956570



Essentials of Statistics for the B...

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 MD = 2.5 points with changed answers. The standard deviation for the difference scores was s = 3.1. Are the data sufficient to conclude that rethinking and changing answers can significantly improve scores? Use a one-tailed test at the .01 level of significance.

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


Given info:

The mean difference MD=2.5, standard deviation is 3.1 and total number in the data set is 22.


The estimate variance using sample variance is


Null hypothesis:

H0:μD=0 (There is no difference between the two tests)

Alternative hypothesis


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