Question

​Let's say that you were going to do an interval on the mean ageof people you should survey to see what they believe about​ self-driving cars. You want to be​ 99% confident that the actual mean is within 2.5 years of the population mean. You know that the population standard deviation of the ages is 7.5 years.

How large a sample do you need to​ have?

​confidence:

standard​ deviation:

​width:

sample​ size:

Answer 1

Given that,

Margin of error (E) = 2.5 years

population standard deviation = 7.5 years

A 99% confidence level has significance level of 0.01 and critical value is,

We want to find, the sample size (n),

Required sample size is 60

confidence = 0.99 or 99%

standard deviation = 7.5 years

Width = 2 * margin of error = 2 * 2.5 = 5 years

Sample size = 60