MATH 225 Week 3 Quartiles and Box Plots Notes

MATH225
Quartiles S Box
Plots

Fractals
Fractals are numbers that partition, or divide, an ordered data set into equal parts.


Quartiles
Divide an ordered data set into 4 equal parts.

a) Arrange data from least to greatest.
b) Find the Median = Q2
c) Even amount of data points—split the data into two equal groups and
find the median of the lower half = Q1. Find the median of the upper half
= Q3.

Odd amount of data points—split the data into two equal groups…do NOT use
the median. Find the median of the lower half = Q1. Find the median of the upper
half = Q3.


Interquartile Range—is a measure of variation that gives the range of the middle
50% of the data. It is the difference between the third and first quartiles.

IQR = Q3 – Q1

Review: Outlier: Data value far removed from data set

IQR Rule: A data value is an outlier if it is above Q3 by an amount greater than
1.5(IQR) or below Q1 by an amount greater than 1.5(IQR).

1. IQR = Q3 – Q1 2. LF = Q1 – 1.5 * IQR 3. UF = Q3 + 1.5 * IQR


Example: Identify any outliers (using the 1.5 x IQR rule).

54, 63, 49, 39, 86, 97, 36, 45, 87, 57, 65, 60, 32, 11, 56
11, 32, 36, 39, 45, 49, 54, 56, 57, 60, 63, 65, 86, 87, 97




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