Calculating percentages from standard deviation

Question

A soccer coach is logging in the number of each soccer members time playeyed on the field.  The average number is 20 minutes  with a standard deviation of 5 . What percentage of players play > or equal to 27 minutes

Answer 1

Compute the Z-score:

 

Z = (x-μ)/σ

• x = the data point = 27
• μ = the mean = 20
• σ = standard deviation = 5

 

Plug in the numbers and compute the Z-score then look it up on a Z-score table (http://www.z-table.com/).  The percent you get is for players  <= 27 minutes.  The number that played > 27 minutes = 1 - the percent from the table.