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 2.5 kwh. the mean electricity usage per family was found to be 16.5 kwh per day for a sample of 3861 families. construct the 98% confidence interval for the mean usage of electricity. round your answers to one decimal place.

Our goal is to collect email addresses from 60% of customers who purchase a product." so that means if i talk to 95 customers, i need to persuade to provide an email address?

2people are trying different phones to see which one has the better talk time. chatlong has an average of 18 hours with a standard deviation of 2 hours and talk-a-lot has an average of 20 hours with a standard deviation of 3. the two people who tested their phones both got 20 hours of use on their phones. for the z-scores i got 1 for the chatlong company and 0 for talk-a-lot. what is the percentile for each z-score?

Bob is putting books on a shelf and takes a break after filling 18 1/2 inches on the book shelf. the book shelf is now 2/3 full. how long is the entire bookshelf?