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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

Hello professor, I am going over Problem 6 of 8.4 and I don't get why when looking for the P value you added? I'm following Problem 1 and thought I had to subtract for P value. Thank you!

Posted to on Saturday, May 16, 2020   Replies: 1


Professor Mcguckian
05/16/2020
9:45 AM EST

Yes, the reason we must add here is that the rule for finding a p-value for a left-tailed test is to find the area to the left of the test statistic. Since the test statistic ended up being a positive value, the test stat is on the right side of the curve. To find the area to the left of the test stat here, we must find the area from that value 1.58 all the way over to the left side's negative infinity. The whole left half of the cure is 0.5000 and the part from 1.58 until the middle of the curve is found from the table. The two parts added together make up the p-value. If the test statistic had been on the left-hand-side of the curve, you would have been looking for a tail area, and it would have been found the way you expected. 

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