Estimation of Population in parameters in z-distribution

1. GreenBot Corporations wants to know the experience of their newly hired employees. Through Human Resource managers they knew that every 20 employees has an experience of 3 years and the standard deviation is 2.7 years. Find the interval estimate of population mean using 90% confidence level.

2. MegaFoods Inc. Tested their new 52 products expiration capability. The average result is 2.4 years and the standard deviation of the samples are 1.1 years. Find the interval estimate of population using 95% confidence level.

3. Students were asked to respond to a survey conducted by school. On average, 15 students took 3 hour responding to the survey and the standard deviation of the sample is 1 hour. Find the Interval estimate of population mean in 99% confidence level.