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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

Professor,
Could you solve step by step the following problem:

A small computing center has found that number of jobs submitted per day to its computers has a distribution that is approximately mound-shaped and symmetric. with a mean of 68 jobs and a standard deviation of 8. Where do we expect approximately 95% of the distribution to fall?

Posted to STATS 1 on Monday, August 19, 2013   Replies: 1


Professor Mcguckian
08/19/2013
5:21 PM EST

Hi Maria,
This problem gives us information that leads us to assume the data is bell shaped, "approximately mound-shaped and symmetric."  As a result, this problem can be done using the empirical rule (especially since it only asks for an approximate answer). 

The empirical rule tells us that approx. two standard deviations will capture 95% of the data, so we need to add 2 standard deviations to the mean and take 2 standard deviations from the mean to create our interval. 

(mean - 2SD, mean + 2SD) = (68 - 2*8, 68 + 2*8) = (68 - 16, 68 + 16) = (52, 84).

I hope that helps,

Professor McGuckian

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