2. A market research firm has been contracted to determine television viewing habits. The firm

selected a random sample of 25 children during a week and obtained a mean of 24 hours and

a standard deviation of 7 hours.

a) State what assumption you must make before you can construct a confidence interval.

b) Construct a 97% confidence interval for the mean number of hours children spend

watching television. Include a statement.

c) The margin or error in part (a) was considered to be too large. What sample size is

required to reduce the margin of error to 1.5 hours or less at 80% confidence level?

Assume the sample standard deviation of 7 hours is a good estimate of the population

standard deviation.

d) The market research has also been asked to estimate what proportion of children watch

television every day of the week with an error of at most 3%, at the 90% confidence

level. What sample size is required to achieve this?