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41. Coping with No Success According to the Rule of Three, when we have a sample size n with x = 0 successes, we have 95% confidence that the true population proportion has an upper bound of 3. (See "A Look at the Rule of Three," by Jovanovic and Levy, American Statistician, Vol. 51, No. 2.) a. If n independent trials result in no successes, why can't we find confidence interval limits by using the methods described in this section? b. If 40 couples use a method of gender selection and each couple has a baby girl, what is the 95% upper bound for p, the proportion of all babies who are boys