Find the value of the 90th percentile of the following set of data
18,9,7,5,11,7,20,19,2,17,12,5,1,13,12,11,15,16,20

Question

Find the value of the 90th percentile of the following set of data
18,9,7,5,11,7,20,19,2,17,12,5,1,13,12,11,15,16,20

directrix · Answer

n = 19 scores
mean = 11.58
pop standard deviation = 5.81

The z-score for the 90th percentile is approximately 1.28.

1.28 = (x - 11.58)/5.81
 x = 19.02 --> The score of 19 is at the 90th percentile.

directrix · Answer

Please check the work above. Tools: Online standard dev and mean calculator http://easycalculation.com/statistics/standard-deviation.php Tutorial on Standard Normal Curve and 90 th Percentile http://tinyurl.com/ahxzwwe Public Domain Tables of Normal Distribution http://www.math.unb.ca/~knight/utility/NormTble.htm