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. Under the null hypothesis that sales are equally divided among the three different covers,what is the value of the expected count for sales of the book with the photograph of the actor on the cover?
A)0.258
B)0.333
C)31
D)40

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.  Under the null hypothesis that sales are equally divided among the three different covers,what is the value of the expected count for sales of the book with the photograph of the actor on the cover?
A)0.258 
B)0.333 
C)31 
D)40

Quizplus · Accepted Answer

Under the null hypothesis, since sales are equally divided among the three choices, the expected count for each cover would be 1/3 of the total sample size (i.e. 120/3 = 40). Therefore, the expected count for sales of the book with the photograph of the actor on the cover would be 40. Hence, the best choice is D.

A Particular Paperback Mystery Book Is Published with a Choice