Suppose that weights of 5th grade elementary boys are normally distributed with mean µ =90 lbs and variance ó2 = 4 lbs. Find the weight that corresponds to Q3 and interpret this measure of position.

Answer 1

Q3 = 75th percentile

Z = (score-mean)/SD

Standard deviation = square root of variance

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the Z score = mean + .25. Insert values into above equation and solve.

I'll leave the interpretation to you.