1. A bank manager wants to estimate the mean amount of interest that credit card holders will pay on their debt. She is trying to decide between the following confidence interval percentages and sample sizes:

Confident interval %	90	95	99
Sample size, n	47	77	236

Advise the bank manager on the combination (oneconfidence interval % andonesample size) that will give the narrowest confidence interval, by placing your choices in the correct positions here:

Confidence interval (%): ?

Sample size: ?

2. In the past, themean number of televisions per household was found to be 2.2. A journalist believes that this has decreased, due to the improvement in the capacity of laptops. In order to test this claim, he took a random sample of 40 households, asking each household, how many televisions they had. He found a mean of 1.7 televisions with a standard deviation of 0.1 televisions. Give the value of the calculated test statistic.

Please give your answercorrectly rounded to two decimal places.

3. A researcher is trying to estimate the population mean time it takes to run a marathon. A random sample of 36 marathon runners was taken from which the mean was found to be 3.42 hours. Assume the population standard deviation is known to be 0.1 hours

a) Construct a 95% confidence interval. SHOW BRIEF WORKINGS to support your answer.

b) Interpret your confidence interval.