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A study of book reviews in American history, geography and area studies was publ

ID: 3255892 • Letter: A

Question

A study of book reviews in American history, geography and area studies was published in Choice magazine. The overall rating stated in each review was ascertained and recorded as follows:
1 = would not recommend,
2 = very little recommendation,
3 = no preference,
4 = recommended and
5 = outstanding contribution.

Based on a sample of 375 book reviews, the probability distribution of rating, X, is:
----------------
X | p(x)
--|-------------
1 | 0.051
2 | 0.099
3 | 0.093
4 | ????
5 | 0.122
-----------------

The probability that a randomly chosen book will have a recommended or higher remark?

Explanation / Answer

P(book will have a recommended or higher remark) = P(X = 4)

                                                                                   = 1 - [P(X = 0) + P(X = 1) + P(X = 2) + P(X = 3) + P(X = 5)]

                                                                                   = 1 - [0.051 + 0.099 + 0.093 + 0.122]

                                                                                   = 0.635 (ans)