posted by kenneth .
a random sample of the grade of 78 students is taken. what is the probability that the average grade will be between 80.3% and 82.3%?
Need a measure of central tendency (mean) and a measure of variability (standard deviation).
Z = (score-mean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to the Z scores.