1. INTERVAL ESTIMATION FOR THE PROPORTION OF A POPULATION:

A bank manager wants to determine the proportion of customers who are paid monthly interest on checking accounts.

A randomsample of 100 clients was selected fromwhich 30 of them earned interest on their accounts. Estimate the proportion of

customers whoare paid interest on their accounts at 90% confidence.

2. ESTIMATION OF THE RANGE OF THE POPULATION MEAN WITH KNOWN POPULATION STANDARD DEVIATION:

A car parts wholesaler needs an estimate of the average life of wipers. Management has determined that the standard deviation

Population is 6 months. In a simple random sample of 100 the average duration was 21 months. At a confidence level of 95% set

an estimate of the half-life of the "wiper".

3. ESTIMATION OF THE RANGE OF THE POPULATION MEAN WITH UNKNOWN POPULATION STANDARD DEVIATION:

One firm is considering moving its operations from the city to the suburbs. One factor to consider is how long it will take employees

get to work. In a survey of 20 employees the average time was 36.5 minutes with a standard deviation of 11.3 minutes. On a level

99% confidence set an estimate of the time it will take employees to get to work.

4. DETERMINE THE SAMPLE SIZE FOR THE PROPORTION:

In a study to be carried out, there is a marked ideathat the proportion is around 70%. Find the required sample size

to estimate the proportion within a margin of error of 3% and a confidence level of 99%.

5. DETERMINE THE SAMPLE SIZE FOR THE MEAN:

Determine the sample size for a study, whose standard deviation is .40, within a margin of error of 2% and a level of

90% confidence