Enjoy learning Statistics Online! Please be sure to share and subscribe to our YouTube channel.

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, Can you please do a video on number 30 from the chapter 8.4 Homework. The test stat was 1.58 and it was a left side test. We look at the Z-table under 1.58 and get .4429, so the P-value would be .5-.4429 =.0571?? in the video i saw that you did both sides of the curve rather then one in like all the other examples can you explain why please?

Posted to STATS 1 on Thursday, April 24, 2014   Replies: 2


Professor Mcguckian
04/24/2014
4:54 PM EST

Hi Allison,

As you stated, it is a left-tailed hypothesis test since Ha has a < symbol.   This means we have to find the area to the left of the test statistic in order to find the p-value, but notice that 1.58 is positive. The test stat, 1.58, is on the right side of the curve. The area to the left of 1.58 is greater than 50% since 1.58 is on the right half of the curve.  When we look up 1.58 we get 0.4429 for the area from 1.58 to 0.  We then have to add 0.5000 to account for the remaining left half of the curve.  The final answer is 0.9429. I'll add a video soon.

Hope that helps,

Professor McGuckian


Professor Mcguckian
04/24/2014
6:54 PM EST

Post a reply / comment below or click here to submit a new question to the forum.