z score statitsics

Question

The electric cooperative needs to know the mean household usage of electricity by its non-commercial customers in kWh per day. Assume that the population standard deviation is  kWh. The mean electricity usage per family was found to be  kWh per day for a sample of  families. Construct the  confidence interval for the mean usage of electricity. Round your answers to one decimal place.

Answer 1

confidence interval = mean +/- z-critical * standard deviation/sqrt(sample size)

in order to determine z-critical we need to know the confidence level, e.g., for a 95% CI z-critical would be 1.96.

We also need the sample as well as the values of the mean and SD in kWh.