Probability: The distribution of incomes for families is....

[lea8802]

The distribution of incomes for families who reside in Fort Dodge is approximately normal with a mean of $55,000 and a standard deviation of $4500. Find the probability that a randomly selected family will have an income:

less than $55,000
less than $45,000
greater than $60,000

I came up with .5000, .0132, and .1335, are these correct? If not how would I come to the correct answer?

 

[tkhunny]

Why not demonstrate how you came to those answers?

 

[lea8802]

How I Came About the Answers!

For less than $55,000 I know that it was .5000, because $55,000 is the mean as well.

For less than $45,000 I got .0132 by taking (45,000-55,000)/4500, which gave me a z-score of -2.22, and then I went to the chart.

For greater than $60,000 I got .1335 by taking (60,000-55,000)/4500, which gave me a z score of 1.11, and when I went to the chart I got .8665, but since it was a greater than problem I had to subtract it from one, which is where I got the solution.

 

[tkhunny]

Looks to me like you have it. Why do you doubt?

Good work.

 

[lea8802]

Math just hasn't ever been my strong point, so I just like to make sure I am not out in left field somewhere. Thank you for all your help.

 

[Pilly151]

Excellent job lea!

Using the standard normal table can be trick until you get the hang of it. It is important to keep in mind the meaning of the problem to keep it all straight.