1. An HR administrator wishes to know the proportion of employees that are currently using a very costly benefit to determine if it is still considered valuable by the staff. If the administrator has no preliminary notion of the proportion of employees using the benefit, how big a sample must she collect to be accurate within 0.13 at the 80% level of confidence? Round up to the next whole number

2. A health insurance broker records the monthly extended health and dental insurance premiums for 18 non-smoking white-collar clients between the ages of 31 and 40 (measured in $):

73	145	47	124	80	96	100	147	126
67	138	124	144	67	153	87	101	136

a. Calculate the sample mean and standard deviation.

x= ?

Round to the nearest cent

s=?

Round to the nearest cent

b. Construct a 80% confidence interval for the mean monthly insurance premium for all non-smoking white-collar clients between the ages of 31 and 40.

? << ?

Round to the nearest cent

3. A sports reporter conducts a study of the fans' overall satisfaction with the sporting event after the event is completed. He surveys 165 randomly selected fans on their way out of the event and asks them to rate their satisfaction with the event on a scale from 0 to 10. The average satisfaction rating is 6.3. It is known from previous studies of this type that the standard deviation in satisfaction level is 2.4. Calculate the margin of error and construct the 98% confidence interval for the true mean satisfaction level for the sporting event.

E=?

Round to three decimal places if necessary

?<

Round to three decimal places if necessary

4. Calculate the margin of error and construct the confidence interval for the population mean using the Student's t-distribution (you may assume the population data is normally distributed).

a. x=88.9,n=64,s=10.3, 90% confidence

E= ?

Round to two decimal places if necessary

?<< ?

Round to two decimal places if necessary

b. x=33.6,n=42,s=14.5, 90% confidence

E=?

Round to two decimal places if necessary

?<

Round to two decimal places if necessary