A Toyota dealer wants to find out the age of their customers (for advertising purposes). They want the margin of error to be 3 years old. Suppose the sigma is 13 years old. If they want a 90% confidence interval, how many people do they need to know about?

Answer 1

90% = mean ± 1.645 SEm

SEm = SD/√n

3 = 1.645 SEm

Answer 2

at least 47