Finding Bone Density Scores. In Exercises assume that a randomly selected subject is given a bone density test. Bone density test scores are normally distributed with a mean of 0 and a standard deviation of 1. In each case, draw a graph, then find the bone density test score corresponding to the given information.
Find P90, the 90th percentile. This is the bone density score separating the bottom 90% from the top 10%.
Step 1 of 1 :
Given the 90th percentile.
The bone density score separating the bottom 90% from the top 10%.
10% = 10/100 = 0.1
90% = 90/100 = 0.9
Here we have to find .
Look in the table A-2 for the value 0.90 (or the value closest) and the z-score in the column/row title is then the corresponding z-score.
z = 1.28