Question

My teacher didn't really explain this well and I just need to understand how to solve this.

Tim Worker is doing his budget. He discovers that the average miscellaneous expense is $45.00 with a standard deviation of $16.00. What percent of his expenses in this category would he expect to fall between $38.60 and $57.80?

The z for $38.60 = - ________

The percent of area associated with $38.60 =_____%

The z for $57.80 =________

The percent of area associated with $57.80 =_____%

Adding the two together, the percent of his expenses between $38.60 and $57.80 is _______%

Answer 1

Formula for z.

Answer 2

@sharpsage

Answer 3

I'll help you get started.

The z for $38.60 = ?

x = 38.60


z = 38.60 - 45
____________
16

z = - 6.40
______
16

z = - .40

Answer 4

The percent of area associated with $38.60 =_____%

What about this?

Do you have a table of areas under the normal curve in your book?

Answer 5

If you would help me help you, then we could knock out this problem.

I need to know this to proceed but you won't tell me.

>>Do you have a table of areas under the normal curve in your book?

Answer 6

Ok, Sorry I was writing everything down.

I think I figured it out

The z for $38.60 = is -0.4
and I for the percentage I got 15.54%
and using the equation for z I got 0.8 for $57.80
and the percent of area associated with $57.80 is 28.81% I think

So 44.35% would be the percent of his expenses between $38.60 and $57.80

Answer 7

@Directrix

Answer 8

What I am asking you is what you are using to get from a z of -.4 to a percentage.

How do you know that >> for the percentage I got 15.54%

I am not saying that it is wrong. I am asking how you got it.

Answer 9

Oh, sorry. The assignment included a table of areas. I didn't see it before.

Answer 10

Okay. That is what I was asking.

Answer 11

You would expect 44.356 per cent to fall between $38.60 and $57.80. Yes.