hi guys, i'm in stats and i can't which equation to use to find this out...


CI = confidence interval
CV = critical value
a = alpha/area

CI = 93%


question: Compute the critical value Za/2 that corresponds to a 93% level of confidence.

This is all I know:

CV = 7%
CV = .07
CVa/2 = .035

the question is compute za/2

so this is what i have

z ( .07 / 2 ) = ?

wtf is z and how do i find it? if you can give me step by step instructions using a calculator that would be greatly appreciated. I use a TI-84 Plus Silver Edition Texas Instruments
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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.jpg

Step 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 1.8
Step 5: Look at the top of the column containing 0.965 0.01
Step 6: Add these two values 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

thank you. your help is greatly appreciated