A population has a mean of 400 and a standard deviation of 50. Suppose a sample of size 125 is selected and is used to estimate . Use z-table.
1) What is the probability that the sample mean will be within +/- 6 of the population mean (to 4 decimals)? (Round z value in intermediate calculations to 2 decimal places.)
My answer was .8413 -.1587= .6826 I followed the same formula For number 2) but got the wrong answer. What am I doing wrong?
2) What is the probability that the sample mean will be within +/- 10 of the population mean (to 4 decimals)? (Round z value in intermediate calculations to 2 decimal places.)