The weights of male babies less than 2 months old in the United States is normally distributed with a mean of 11.5 pounds and a standard deviation of 2.7 pounds.

Question

Find the 80th percentile score for these weights.

Answer 1

Try z-scores:

z = (x - mean)/sd

Substitute the data into the above formula and solve for x.

mean = 11.5
sd = 2.7
z = score from the table

Use the table to find z-score at the 80th percentile.

I'll let you take it from here.