Riemann surface
matlab

AP统计学考试准备：AP统计学考试的重点和要求，解题策略和技巧，模拟考试和练习题的解析等。

A pet food manufacturer runs an experiment to determine whether three brands of dog food ae equally preferred by dogs. In the experiment, 150 dogs are individually presented with three dishes of food, each containing a different brand, and their choices are noted. Tabulations show that 62 dogs go to brand A, 43 to brand $\mathrm{B}$, and 45 to brand $\mathrm{C}$. Is there sufficient evidence to say that dogs have preferences among the brands? Test at the $10 \%$ significance level.

(A) No, with $\chi^2=2.09$, there is not sufficient evidence even at the $25 \%$ significance level.
(B) No, with $\chi^2=4.36$, there is not sufficient evidence at the $10 \%$ level.
(C) No, with $\chi^2=19.0$, there is not sufficient evidence even at the $0.1 \%$ level.
(D) Yes, with $\chi^2=4.36$, there is sufficient evidence at the $10 \%$ level.
(E) Yes, with $\chi^2=19.0$, there is sufficient evidence even at the $0.1 \%$ level.

The American Medical Association (AMA) wishes to determine the percentage of obstetricians who are considering leaving the profession because of the rapidly increasing number of lawsuits against obstetricians. How large a sample should be taken to find the answer to within $\pm 3 \%$ at the $95 \%$ confidence level?

(A) 6
(B) 33
(C) 534
(D) 752
(E) 1068

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