Question

3) A random sample of 420 American teens finds that they spend an average of 7.2 hours per day using screens, with a standard deviation of 2.4 hours.

a) Use the 2SD method to find a 95% confidence interval estimate of the average (mean) hours of screen time that American teens use per day. Show all work/steps to get the 2SD estimate. Round your margin of error to three decimal places. Work and Answer:

b) A cell phone company claims that people are exaggerating the amount of screen time that American teenagers are actually using, and the cell phone company instead claims that American teens actually use less than 4 hours of screen time on average per day. Assuming the sample discussed above was truly a representative sample of American teenagers, what would be an accurate response to this claim? Does the claim seem accurate or inaccurate? Clearly explain. Work and Answer:

c) If I now told you that it was actually a sample with only 42 American teens (instead of 420 as I originally stated), but we still got the same sample mean and the same sample standard deviation, then would our new adjusted 95% confidence interval be wider, or would it be narrower than the original confidence interval? Work and Answer:

Answer 1