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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 encountered a couple of problems in section 5.2 hw when they ask to find the probability between numbers. Number 20, asks for the probability for a randomly selected dieter on the plan he is on to loose between 5 and 10 pounds. So when i draw it, i shade in what is between 5-10, but then there is 2 empty spaces everything below 5 and after 10, so I am not sure how i am supposed to calculate after i get the z scores?

Then 25) its finding the probability between 145 and 146, so I find the z score for 145, which is 0.4207, and 146 is 0.2673, now what calculation do i have to do because i am stuck in the same position as #20, since is it a shaded part in the same side, i do not know what to do, maybe i am shading wrong?

Then for 29) I get that z score of 0.2486 and 0.4032, and i was adding them, but it is the wrong answer. I shaded between 110 and 120 on the right side?

31) I found the z scores as well 0.4192 and 0.3413, but i do not know what to do with the numbers, since i shaded in between 155 and 165.

Thank you in advance,
Natassia

Posted to STATS 1 on Saturday, November 2, 2013   Replies: 1


Professor Mcguckian
11/02/2013
9:43 AM EST

Hi Natassia,

In each of the questions you are asking about, the problems deal with what I call the "Same-Side-Subtract" case. If you have two z-scores on the same side of the curve, and you are shading between them, you will subtract the probability values from the z-table to solve the problem.

The attached video deals with this case. Let me know if you have any further questions on this topic.

Professor McGuckian

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