单选题 Gus Hayden, CFA, has developed a mutual fund selection product based on historical information from 2000-2010 period and performs a hypothesis test about performances of different styles. In order to minimize the probability of both Type Ⅰ and Type Ⅱ error, Hayden should increase the:
A. the power of a test.
B. level of significance.
C. sample size.

【正确答案】 C

【答案解析】[解析] 同时减少第一类去真错误和第二类存伪错误的办法只有增加样本的容量。检验效力(the power of a test)是1减去犯第二类存伪错误的概率。