Question

A marketing specialist wants to estimate the average amount spent by visitors to an online retailers...

A marketing specialist wants to estimate the average amount spent by visitors to an online retailers newly-designed website. From the data in a preliminary study she guesses that the standard deviation of the amount spent is about 14 dollars.

Question 1. How large a sample should she take to estimate the mean amount spent to within 5 dollars with 90% confidence? (Round your answer up to the next largest integer).

Homework Answers

Answer #1

Solution :

Given that,

Population standard deviation = = 14

Margin of error = E = 5

At 90% confidence level

= 1-0.90% =1-0.90 =0.10

/2 =0.10/ 2= 0.05

Z/2 = Z0.05 = 1.645

Z/2 = 1.645  

Z/2 = 1.645

sample size = n = [Z/2* / E] 2

n = [1.645 * 14 /5 ]2

n = 21

Sample size = n = 21

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