The branch manager of a pet supply store wants to study characteristics of custo

Question

The branch manager of a pet supply store wants to study characteristics of customers of his store. In particular, he decides to focus on two variables: the amount of money spent by customers and whether the customers own only one cat. 7. (5 points) If he wants to have 95% confidence of estimating the true population mean amount spent in his store within ± $1.50 and the standard deviation is assumed to be $10, what sample size is needed? Show your calculations 8. (5 points) If he wants to have 90% confidence of estimating the population proportion of customers who own only a cat to within ± 0.045, what sample size is needed? Show your calculations

Explanation / Answer

7. For 95% CI critical value is 1.96

n=1.962*sd2/E2=3.84*100/2.25=170.73=171

8. For proportion

Conservative Method

n=z2*1/2.1/2/E2

This formula can be obtained from part (a) using the fact that:

For 0 p 1, p (1 - p) achieves its largest value at

For 90% CI critical value is 1.645

n=1.6452*0.5*0.5/0.0452=334

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