A researcher wants to know if the mean Body Mass Index (BMI) among a group of college students differs from 22. He took a random sample of 20 students and obtained their BMI:
22 21 21 22 26 24 20 24 24 27
36 28 20 25 22
19 24 26 22 21
Find the mean first = sum of scores/number of scores
Subtract each of the scores from the mean and square each difference. Find the sum of these squares. Divide that by the number of scores to get variance.
Standard deviation = square root of variance
Z = (score-mean)/SEm
SEm = SD/√n
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to the Z score. How does it compare to whatever level of significance you are using?