Can someone give me simple formulas for the below problems. What I found is too confusing.

Question

A sample of 145 values is randomly selected from a population with mean, ì, equal to 45 and standard deviation, ó, equal to 23. (Give your answers correct to one decimal place.)
(a) Determine the interval (smallest value to largest value) within which you would expect 99.7% of such sample means to lie.
to

(b) What is the amount of deviation from the mean for a sample mean of 50?


(c) What is the maximum deviation you have allowed for in your answer to part (a)?

Answer 1

a) 99.7% = mean ± 2.96 SEm

SEm = SD/√n

b) SEm = SD/√n

c) See a.

Answer 2

thanks for the above but it still does not work out for me 45+2.96=47.96, 45-2.96=42.04 I don't think I understand this one