Thread: Stats: probability and zscores help

1. Stats: probability and zscores help

Im looking back over an old assignment and I cant figure out how to get the correct probability

Question: what is the probability of encountering a state with annul income less than ore equal to Maine?

Maine: (19590- 21856)/3537.59= - .64
(Maines income - mean) / standard deviation

go to the ztable, and the area associated with -.64 is .2611

then somehow I came up with a probability value of 26.43%, which is the correct answer but I have no idea how to get this probability value.

2. Originally Posted by cmf0106
Im looking back over an old assignment and I cant figure out how to get the correct probability

Question: what is the probability of encountering a state with annul income less than ore equal to Maine?

Maine: (19590- 21856)/3537.59= - .64
(Maines income - mean) / standard deviation

go to the ztable, and the area associated with -.64 is .2611

then somehow I came up with a probability value of 26.43%, which is the correct answer but I have no idea how to get this probability value.

Pr(Z < -0.64) = Pr(Z > 0.64) = 1 - Pr(Z < 0.64) = 0.2611. I assume you got Pr(Z < 0.64) from tables ......

To get a percentage, mutiply by 100.

I don't know where 26.43% has come from .....