The head of the quality control department at a publishing company is studying the effects of the type of glue and the type of binding on the strength of the bookbinding. The company has three possible glues to choose from and the book can either be bound as a paperback or a hardback. Many stacks of books are ready to be bound—some in paperback form, some in hardback form. As part of this study, 45 books are to be randomly selected from each type of binding and then randomly assigned to one of the three types of glue. What type of sampling method is being used to select the books?
a. Simple random sample
b. Stratified sample
c. Multistage sample
d. Block sample
e. Convenient sample
And can you tell me why the other choices are wrong.

According to my research on different sampling methods, I can say that based on the information provided within the question the sampling method being used in this scenario is a Stratified method. This method is when researchers divide the subjects or what is being sampled into groups and then randomly draws from each group. Which is what is happening here since the glues are divided into three different types and then each book is applied with a randomly selected glue.

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