Lecture Goals

You should be able to:
    - calculate and explain the range
    - use the IQR rule to test for outliers
    - calculate the variance and standard deviations for pop. and samples
    - explain the theory variance and S.D are based on

Reading

Chapter 4
 

Student Class A Class B
1             80             60
2             80             60
3             80           100
4             80           100
 

Mean of each set of scores is 80

Median of each set of scores is 80

Sometimes 2 __________________ data sets have similar means and medians

Impairs descriptions and ___________________

Q - How do the scores from each class differ?
 

Answer
1) ________________
 

Class A Histogram
 
 
 
 
 
 
 

Class B Histogram
 
 
 
 
 
 
 

Range = measure of _______________
 

Range = max. value - min. value = _____________________
 
 

Range and Extreme Values
 
 
 
 
 
 
 
 

Range

Using the range to Identify Outliers

Visually inspect a scatter plot

IQR rule
 

Identifying Outliers

Visual inspection
 
 
 
 
 
 
 
 
 
 
 

Interquartile Range Rule
 

Step 1: Find ____, _____, ________
 
 
 
 
 
 
 
 
 

Step 2: Find median of #s from min to median and ___________________
 
 
 
 
 
 
 
 
 
 

Step 3: Find median of #s from median to max and __________________
 
 
 
 
 
 
 
 

Step 4: Label median _________
 
 
 
 
 
 
 
 

Self Check

min - Q1 = 25%
Q1 - Q2(md) = 25%
 

Q2(md) - Q3 = 25%
Q4 - max = 25%
 
 
 
 

Interquartile range = _______________________________
 

Multiply IQR by ___________
 
 
 
 

Outlier if:

Greater than [median + (IQR *1.5) ]
 
 
 
 
 

Less than [median - (IQR *1.5)]