Hey all Its been a while since Ive taking a probability cour

Hey all,

It\'s been a while since I\'ve taking a probability course and I\'m really stuck on how to deal with getting values from a normal table that have a thousandths digit. Is there a formula for dealing with this?

Ie; For N(.875) I found I could get the right answer by taking N(.87) + N(.88) and dividing that by 2. How would I deal with something like N(.888)?

-Please explain and show the work!!

Solution

Hi!

Unfortunately, there is no formula for this.

You can use some form of technology, like a ti-84 calculator (normcdf function), or Microsoft Excel.

To get the left tailed area for a z score in Excel, you can type on any cell

=NORMSDIST(z)

In your case, to get the left tailed area of 0.888, just type

=NORMSDIST(0.888)

and it will give you 0.812729624. [done!]