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Transcript
I can identify and draw conclusions with
mean, median, percentile, quartiles, range,
standard deviation, variance, inter-quartile
range and outliers.
1
Ch. 1 Day 3 Sec 1.2
Mean = Average
"x­bar"
or
Median M = Midpoint
1. Order Sm to Lrg
2. If odd # of observations, middle #
3. If even # of observations, mean of 2 middle numbers
* Median is not affected (as much)by outliers. The mean is affected by outliers.
Find the Mean and Median
Ex. 2, 4, 8, 10 now compare to data 2, 4, 8, 10, 26
2
Find the Mean and Median with the TI ­ 84
IQ Test scores 11 randomly selected 7th graders.
114, 100, 104, 89, 102, 91, 114, 114, 103, 105, 108
Mean
Sum of the observations
Sum of the observations squared
Standard Deviation
Population Deviation
Number of Observations
3
If data is exactly symmetric the mean = median
M
If data is skewed left, mean < median
M
If data is skewed right, mean > median
M
4
5 Number Summary
Min, Q1, Med, Q3, Max
When to use? When you have
skewed data, using the Median to
describe the center.
IQR ­ Inter Quartile Range Q3 ­ Q1 Spread of the middle 50%
Outlier ­ If a point is more than 1.5(Q3 ­ Q1) from Q1 or Q3, then it is an outlier
Find the 5 # summary for the number of HR's hit by Barry Bonds
16 19 24 25 25 33 33 34 34 37 37 40 42 46 49 73
Draw a Boxplot with the 5 # summary
5
Find the 5 # summary for the number of HR's hit by Barry Bonds with the TI
16 19 24 25 25 33 33 34 34 37 37 40 42 46 49 73
Draw a Boxplot with the TI
6
Standard Deviation
Used to describe the spread of data when
using the mean to describe the center.
Standard Deviation is the average spread of
data from the mean.
n-1 represents the degrees of freedom
When s=0, there is no spread
s>0 Always! Why?
As observations become more spread out,
s will increase.
Variance - is the Standard Deviation
squared
7
I can identify and draw conclusions with mean,
median, percentile, quartiles, range, standard
deviation, variance, inter-quartile range and
outliers.
8