Question

An analyst is reviewing a dataset of temperatures recorded at airports in the U.S. In a random sample of 87 airports, she finds the average summer temperature to be 87 degrees Fahrenheit. What value of z should be used to calculate a confidence interval with a 95% confidence level?

Answer 1

We use z = 1.96

Explanation:

We have that to find our
`\alpha` level, that is the subtraction of 1 by the confidence interval divided by 2. So:

`\alpha = (1-0.95)/(2) = 0.025`

Now, we have to find z in the Ztable as such z has a pvalue of
`1-\alpha`.

So it is z with a pvalue of
`1-0.025 = 0.975`, so
`z = 1.96`

We use z = 1.96