1. A time study was conducted for a job that has a mean of 21 and a standard deviation of 2.5. If we require that our estimate of the Observed Time be within 3 % with a level of confidence of 98%, how many observations are required?

2. A time study was conducted for a job that has a mean of 21 minutes and a standard deviation of 2.5 minutes. If we require that our estimate of the Observed Time be within 0.4 minutes with 90% accuracy, how many observations are required?

3. In an analysis designed to estimate how often call center operators were idle, 90 observations were made. Operators were idle 37 times.

What is the estimated percentage of idle time?

4. In an analysis designed to estimate how often call center operators were idle, 90 observations were made. Operators were idle 37 times.

Based on the initial results, approximately how many observations would you require to estimate the actual percentage idle time, within 3 % with a confidence of 95%.

Z- Confidence value 90% 1.65 95% 1.96 95.5% 2.00 98% 2.33 99% 2.58