This isn't something you can do with just a calculator. You need to use a Z table, found here:
http://i.imgur.com/S1XEi.jpgStep 1: Calculate the 0.035 that you already know how to do.
Step 2: Calculate 1-0.035 = 0.965
Step 3: Look at the Z table and find 0.965 (or as close to this value as possible)
Step 4: Look at the far left of the row containing 0.965
![-->](http://forums.d2jsp.org/html/emoticons/icon_pointr.gif)
1.8
Step 5: Look at the top of the column containing 0.965
![-->](http://forums.d2jsp.org/html/emoticons/icon_pointr.gif)
0.01
Step 6: Add these two values
![-->](http://forums.d2jsp.org/html/emoticons/icon_pointr.gif)
1.81
Step 6 is your z value that corresponds to that level of confidence.
Edit: More correctly, you CAN do it with your calculator using that formula, but there's absolutely no reason to do so when you have the Z table.
This post was edited by bentherdonethat on Nov 23 2011 02:33am