Question

How do I find a Z score when given the area? An example would be 0.45 = a Z score of -0.13

Answer 1

are you allowed to use a calculator like a TI83 or TI84?

Answer 2

We have to show all our work on paper.

Answer 3

This is one of those problems where you have to use a table or a calculator. Doing so by hand would take way too long.

Answer 4

I have the tables. They came along with my book. I just have no clue how to find the Z score for an area. :/

Answer 5

ok what you do is look in the table for the value 0.45 or close to it

for example, in this table

http://www.stat.ufl.edu/~athienit/Tables/Ztable.pdf

the value 0.4522 is in the second to last row, 4th column
the value 0.4522 is as close as we can get to 0.4500
it corresponds to a z-score of -0.12 since it is in the `-0.1` row and `0.02` column

so basically that this means is

\[\Large P(Z < -0.12) \approx 0.4500\]

Answer 6

actually 0.4483 is closer to 0.4500
so instead of -0.12 it should be -0.13

Answer 7

see attached

Answer 8

So I look for the closest number in the chart, without going over that value? Then find the Z code for that?

Answer 9

just the closest in general

Answer 10

I got it right! Thank you so much. I have been having issues with this since this morning.

Answer 11

|0.4522 - 0.4500| = 0.0022
|0.4483 - 0.4500| = 0.0017

so 0.4483 is closer to 0.4500 meaning that z = -0.13 is slightly more accurate

Answer 12

you're welcome