Question

Bob Nale is the owner of Nale's Gas Station. Bob would like to estimate the mean number of gallons of gasoline sold to his customers. He assumes a population standard deviation of 2.30 gallons. From his records, he selects a random sample of 60 sales and finds the mean number of gallons sold is 8.60. What is the z-statistic for a 99% confidence interval for the population mean.

Answer 1

Answer:

The z-statistic for a 99% confidence interval for the population mean is 2.575.

Step-by-step explanation:

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

$\alpha = \frac{1 - 0.99}{2} = 0.005$

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

That is z with a pvalue of $1 - 0.005 = 0.995$, so Z = 2.575.

The z-statistic for a 99% confidence interval for the population mean is 2.575.