When calculating a confidence interval for the mean using a sample size of 30 or more with a known population standard deviation, the is used.

Z critical value

Step-by-step explanation:

given that we are calculating confidence interval.

The sample size is greater than or equal to 30.

Population standard deviation is known.

Whenever we know the population standard deviation and also when sample size is atleast 30, we can safely use Z critical value.

This is based on the assumption that the distribution of the mean is normal.

Hence we use the Z critical value arrived from standard normal distribution table.

Normally for two tailed we use 1.645, 1.96 and 2.58 for 90%, 95% and 99% respectively

When calculating a confidence interval for the mean using a sample size of 30 or more with a known population standard deviation, the _Z critical value is used.

answer: .75 km

step-by-step explanation:

boxplot