Question

The speaker converts x=250 to z=1.67 using the z-score formula.  Using the z-table in back of book he determines  P(X>250)  = .0475. If you used the NORMALCDF(?,?,?,?) what would your answer be taken 5 decimal places (the answer is slightly different)?

Answer 1

The mean of standard normal distribution is 0 and standard deviation is 1

Here we want to find P( X > 250) = P( Z > 1.67)

Let's use TI-84 Plus calculator

2ND >>>VARS >>>2:normalcdf( >>> ENTER

Fill the necessary information:

Look the following image:

Then highlight Paste and press ENTER

again press ENTER

So we get the following output:

So answer up to five decimal places is as P(X > 250) = P( Z > 1.67) = 0.04746