QUESTION 1

Niagara College conducted a study to determine how much students speny on books each semester. A sample of 14 students revealed a mean of $239 with a standard deviation of $26 Construct a 90% confidence interval for the mean amount spent on books each semester by students. (Round your lower and upper limits to two decimal places)

QUESTION 2

A company is considering purchasing sodium lights from a firm. The company wishes to estimate the mean life of the lights before placing the order. A preliminary check indicates that the mean life of the lights is 20,000 hours with a standard deviation of 1,500 hours. If the company wishes to estimate the mean life of the lights within 200 hours, with a confidence level of 98%, how many lights should be tested?

QUESTION 4

A social media company conducted a study to find out what proportion of people log in to their account every day. A sample of 800 accounts showed that 624 logged in every day. Construct a 95% confidence interval for the population proportion that log in every day to their account. (Round your lower and upper llimits to three decimals)

What was the lower limit of your interval?

QUESTION 5

A credit card company wants to estimate the true proportion of people who will sign up for a new card that they are introducing. The company feels that based on past results, when new cards were introduced, the proportion who will sign up will be 0.28. If the company wants to be 95% confident that they are within 4.5% of the true proportion, how many people should they survey?