Hi. I just took the test for unit 2 of MA121 Introduction to Statistics.

The last question goes like this:

Suppose that the average income in the population in City X is $50,000 with a standard deviation of $10,000. Calculate the z-score for a person that earns less than $45,000, assuming that income is normally distributed.

It should be very straightforward:

- Z = -0.5
- Go to the table and check the value for -0.5, which is 0.3085.

But I got the answer wrong, and instead the correct solution is much lower.

I cannot find what I am doing wrong. I have also tried with a Ti-36X and I also get 0.3085.

Thank you for hour help.

A.