Why would it be better to initiate research from a specific hypothesis than from a broad topic?

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1. Why would it be better to initiate research from a specific hypothesis than from a broad topic?
2. In what type of circumstances would it be better to avoid a Type I error as opposed to trying to avoid a Type II error?
3. Various ethical issues are presented in Chapters 7, 8, 9, and 10 (prior to Summary).  Which do you feel to be more important, especially in dealing with human subjects, and why?