# standard deviation

#### saige30

##### New Member
I have a problem I'm struggling to figure out how to compute....could someone walk me though the problem and explain how to figure out the answer? I'm really not even sure where to start on these types of problems. Thanks!

problem: The average sales representative for Insmed pharmaceutical company earns $124,000 in sales incentives with a standard deviation of$32,000. Assuming that the salaries are normally distributed, 90% of teh salaries will be above what dollar mark?

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#### Dragan

##### Super Moderator
I have a problem I'm struggling to figure out how to compute....could someone walk me though the problem and explain how to figure out the answer? I'm really not even sure where to start on these types of problems. Thanks!

problem: The average sales representative for Insmed pharmaceutical company earns $124,000 in sales incentives with a standard deviation of$32,000. Assuming that the salaries are normally distributed, 90% of teh salaries will be above what dollar mark?
Use the Z-tranformation: Z = (X - Mu)/Sigma.

You know that Mu = 124, Sigma = 32, and from the Z-table Z = -1.28. Solving for X we obtain X = 32*(-1.28) + 124= your answer...(multiply your answer times 1000 to get the dollar amount).

z score