A random check of 81 records of inmates from all federal prisons found the confidence interval for mean prison terms per prisoner to be 2.113 years to 2.287 years. Assuming a standard deviation of 0.4 year, what is the level of confidence provided by this interval?
Mean= M = 2.2 years =(2.113+2.287)/2
assuming mean to be midway between upper confidence limit and lower confidence limit
Standard deviation =s = 0.4 years
The confidence level for an interval estimate is calculated.