Question

A fashion designer wants to know how many new dresses women buy each year. Assume a previous study found the standard deviation to be 1.2. She thinks the mean is 7.9 dresses per year. What is the minimum sample size required to ensure that the estimate has an error of at most 0.12 at the 90% level of confidence? Round your answer up to the next integer.

Answer 1

Answer:

Atleast 271

Step-by-step explanation:

Given that a  fashion designer wants to know how many new dresses women buy each year. Assume a previous study found the standard deviation to be 1.2.

Mean =7.9

For margin error to be at most 0.12

we have for 90% confidence level

$1.645*\frac{1.2}{\sqrt{n} } \leq 0.12\\\sqrt{n}\geq 16.45\\n\geq 270.6\\n\geq 271$