PRACTICE OF STATISTICS F/AP EXAM
PRACTICE OF STATISTICS F/AP EXAM
6th Edition
ISBN: 9781319113339
Author: Starnes
Publisher: MAC HIGHER
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Chapter 2.2, Problem 66E
To determine

Percentage of observations that are classified as outliners by the 1.5×IQR rule.

Expert Solution & Answer
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Answer to Problem 66E

0.74% of the observations are classified as outliners by the 1.5×IQR rule.

Explanation of Solution

Given information:

Observations are classified as outliners by 1.5×IQR rule.

In the appendix, the standard normal table consists of the probabilities for the values smaller than z − score and also the probabilities to the left of z − score.

The property of 1st quartile reveals that 25% of the data values are below it.

The property of 3rd quartile reveals that 75% of the data values are below it.

The z − score corresponding to the probability of 25% (or 0.25) and 75% (or 0.75) in the normal probability table of the appendix:

  z=±0.67

Then

The quartile is the mean increased by the product of z − score and standard deviation.

  Q=μ±zσ=μ±0.67σ

Interquartile range is the difference between the 3rd and 1st quartile.

  IQR=Q3Q1=μ+0.67σ(μ0.67σ)=1.34σ

Multiply both sides by 1.5:

  1.5IQR=1.5(1.34σ)=2.01σ

Now,

Outliers are more than 1. 5IQR below the 1st quartile (Q1) .

Or

Outliers are more than 1. 5IQR above the 3rd quartile (Q3) .

Thus,

  Q11.5IQR=μ0.67σ2.01σ=μ2.68σ

Or

  Q3+1.5IQR=μ+0.67σ+2.01σ=μ+2.68σ

Then

The corresponding probability,

  P(z<2.68orz>2.68)=2×P(z<2.68)=2×0.0037=0.0074=0.74%

Therefore,

0.74% of the observations are classified as outliners by the 1.5×IQR rule is same in any Normal distribution.

Chapter 2 Solutions

PRACTICE OF STATISTICS F/AP EXAM

Ch. 2.1 - Prob. 11ECh. 2.1 - Prob. 12ECh. 2.1 - Prob. 13ECh. 2.1 - Prob. 14ECh. 2.1 - Prob. 15ECh. 2.1 - Prob. 16ECh. 2.1 - Prob. 17ECh. 2.1 - Prob. 18ECh. 2.1 - Prob. 19ECh. 2.1 - Prob. 20ECh. 2.1 - Prob. 21ECh. 2.1 - Prob. 22ECh. 2.1 - Prob. 23ECh. 2.1 - Prob. 24ECh. 2.1 - Prob. 25ECh. 2.1 - Prob. 26ECh. 2.1 - Prob. 27ECh. 2.1 - Prob. 28ECh. 2.1 - Prob. 29ECh. 2.1 - Prob. 30ECh. 2.1 - Prob. 31ECh. 2.1 - Prob. 32ECh. 2.1 - Prob. 33ECh. 2.1 - Prob. 34ECh. 2.1 - Prob. 35ECh. 2.1 - Prob. 36ECh. 2.1 - Prob. 37ECh. 2.1 - Prob. 38ECh. 2.1 - Prob. 39ECh. 2.1 - Prob. 40ECh. 2.2 - Prob. 41ECh. 2.2 - Prob. 42ECh. 2.2 - Prob. 43ECh. 2.2 - Prob. 44ECh. 2.2 - Prob. 45ECh. 2.2 - Prob. 46ECh. 2.2 - Prob. 47ECh. 2.2 - Prob. 48ECh. 2.2 - Prob. 49ECh. 2.2 - Prob. 50ECh. 2.2 - Prob. 51ECh. 2.2 - Prob. 52ECh. 2.2 - Prob. 53ECh. 2.2 - Prob. 54ECh. 2.2 - Prob. 55ECh. 2.2 - Prob. 56ECh. 2.2 - Prob. 57ECh. 2.2 - Prob. 58ECh. 2.2 - Prob. 59ECh. 2.2 - Prob. 60ECh. 2.2 - Prob. 61ECh. 2.2 - Prob. 62ECh. 2.2 - Prob. 63ECh. 2.2 - Prob. 64ECh. 2.2 - Prob. 65ECh. 2.2 - Prob. 66ECh. 2.2 - Prob. 67ECh. 2.2 - Prob. 68ECh. 2.2 - Prob. 69ECh. 2.2 - Prob. 70ECh. 2.2 - Prob. 71ECh. 2.2 - Prob. 72ECh. 2.2 - Prob. 73ECh. 2.2 - Prob. 74ECh. 2.2 - Prob. 75ECh. 2.2 - Prob. 76ECh. 2.2 - Prob. 77ECh. 2.2 - Prob. 78ECh. 2.2 - Prob. 79ECh. 2.2 - Prob. 80ECh. 2.2 - Prob. 81ECh. 2.2 - Prob. 82ECh. 2.2 - Prob. 83ECh. 2.2 - Prob. 84ECh. 2.2 - Prob. 85ECh. 2.2 - Prob. 86ECh. 2.2 - Prob. 87ECh. 2.2 - Prob. 88ECh. 2.2 - Prob. 89ECh. 2.2 - Prob. 90ECh. 2.2 - Prob. 91ECh. 2.2 - Prob. 92ECh. 2 - Prob. R2.1RECh. 2 - Prob. R2.2RECh. 2 - Prob. R2.3RECh. 2 - Prob. R2.4RECh. 2 - Prob. R2.5RECh. 2 - Prob. R2.6RECh. 2 - Prob. R2.7RECh. 2 - Prob. R2.8RECh. 2 - Prob. R2.9RECh. 2 - Prob. T2.1SPTCh. 2 - Prob. T2.2SPTCh. 2 - Prob. T2.3SPTCh. 2 - Prob. T2.4SPTCh. 2 - Prob. T2.5SPTCh. 2 - Prob. T2.6SPTCh. 2 - Prob. T2.7SPTCh. 2 - Prob. T2.8SPTCh. 2 - Prob. T2.9SPTCh. 2 - Prob. T2.10SPTCh. 2 - Prob. T2.11SPTCh. 2 - Prob. T2.12SPTCh. 2 - Prob. T2.13SPT
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