A particular paperback mystery book is published with a choice of three different pictures on the cover: a photograph of the actor playing the main character in the movie version of the book,a drawing of the mansion where the story takes place,or an embossed graphic of the murder weapon.A certain bookstore keeps copies of this book with each of the pictures on the cover on its racks.To test the hypothesis that sales of this book are equally divided among the three choices,a simple random sample of 120 purchases of this book is obtained.The numbers are displayed in the table below. What are the appropriate degrees of freedom for the chi-square statistic under the null hypothesis that sales are equally divided among the three different covers?
A)1
B)2
C)3

Question

A particular paperback mystery book is published with a choice of three different pictures on the cover: a photograph of the actor playing the main character in the movie version of the book,a drawing of the mansion where the story takes place,or an embossed graphic of the murder weapon.A certain bookstore keeps copies of this book with each of the pictures on the cover on its racks.To test the hypothesis that sales of this book are equally divided among the three choices,a simple random sample of 120 purchases of this book is obtained.The numbers are displayed in the table below.  What are the appropriate degrees of freedom for the chi-square statistic under the null hypothesis that sales are equally divided among the three different covers?
A)1 
B)2 
C)3

Quizplus · Accepted Answer

The degrees of freedom for chi-square are calculated as (number of rows - 1) x (number of columns - 1). In this case, there are 3 choices of covers, so there are 3 columns. The sample data table shows only one row, so the number of rows is 1. Therefore, the degrees of freedom are (1-1) x (3-1) = 2.

A Particular Paperback Mystery Book Is Published with a Choice