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ASK THE PROFESSOR FORUM

Course Documents

Chapter 1 - Intro

Chapter 2 - Methods for Describing Sets of Data

Chapter 3 - Probability

Chapter 4 - Discrete Random Variables

Chapter 5 - Normal Random Variables

Chapter 6 - Sampling Distributions

Chapter 7 - Confidence Intervals

Chapter 8 - Tests of Hypothesis: One Sample

Chapter 9 - Confidence Intervals and Hypothesis Tests: Two Samples

Sample Exam I: Chapters 1 & 2

Sample Exam II: Chapters 3 & 4

Sample Exam III: Chapters 5 & 6

Sample Exam IV: Chapters 7 & 8

Ask the Professor Forum

Hi professor, I have a small question on the now you try it 7.2 problem 1
the confidence level is .99 so when I look for Z I would divide .01/2 and get .005 and look that up in the T-Table but in this particular problem we do not we simply look up .01 on the the t-table why is that?

Posted to STATS 1 on Wednesday, December 11, 2013   Replies: 1


Professor Mcguckian
12/11/2013
8:47 PM EST

Hi Natasha,

We divide the alpha by two because our confidence intervals are two-sided intervals. You'll notice on your formula card, we use the notation Za/2. The alpha/2 is telling you that you must always divide alpha by two when constructing a confidence interval.

Hope that answers your question,

Professor McGuckian

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