The standard deviation for a population is sigma = XXXXXXXXXXA sample of 21 observations selected from this population gave a mean equal to XXXXXXXXXXThe population is known to have a normal...

The standard deviation for a population is sigma = 14.8 . A sample of 21 observations selected from this population gave a mean equal to 142.55 The population is known to have a normal distribution Make a 99% confidence interval for Construct a 97% confidence interval for a 95% confidence interval