# Percentiles and Z- Scores

1. Oct 17, 2004

### majinknight

Hi i am having trouble with a couple questions involving percentiles, here is the question:

1) Adrian's average bowling score is 174, with a standard deviation of 35.
a) In what percent of games does Adrian score less than 200 points? More than 200 points?
b) The top 10% of bowlers in Adrian's league get to play in an all-star game. If the league average is 170, with a standard deviation of 11 points, what average score does Adrian need to have to obtain a spot in the all-star game?

Thank you.

2. Oct 17, 2004

### Tide

Use the definition of Z-score:

$$Z = \frac {x - \bar x}{\sigma}$$

and use your textbook tables for cumulative probability (or words to that effect depending on the authors).

3. Oct 18, 2004

### majinknight

I figured it out now, you had to use this Z-score table in the back of the text book which i did not know how to do. Thanks for the help though.