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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

For Homework 7.4 For number 42 n=128 so n-1=127 that number isnt on the t-table so how would you solve it? Also for homework 7.4 if the sample size is 30 or greater do we use the z-table?

Posted to STATS 1 on Friday, November 15, 2013   Replies: 2


Professor Mcguckian
11/16/2013
11:20 AM EST

Hi Natalie,

In that section, you are trying to distinguish between when to use a z-critical value or a t-critical value. Remember, we are using the simplified rule that states if n > 30, we will find a z-critical value, otherwise we will find a t-critical value. For example, in the problem you asked about, since n = 128, we need a z-critical value, so you do not need to find degrees of freedom to find the 1.282.

Hope that answers your question,

Professor McGuckian


.
11/17/2013
6:29 PM EST
Ok thank you.

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