Download 7.3 Measures of Central Tendency and Measures of Dispersion

7.3
(Purple)
Measures of Central Tendency
and
Measures of Dispersion
Midterm: Oct. 6
Vocabulary
• Statistics:
Are numerical values used to
summarize and compare sets of data.
Vocabulary
• Measure of Central Tendency
Is a number used to represent the
center or middle of a set of data
values.
• What are the measures of central
tendency?
Mean ( x ), Median, and Mode
Vocabulary
• Measures of Dispersion
Is a statistic that tells you how
dispersed, or spread out, data
values are.
• What are the measures of dispersion?
Range, Mean Deviation, Variance,
and Standard Deviation
Measures of Dispersion we will
look at today:
• Range: highest value – lowest value
• Standard Deviation:

 x1  x 
Symbol:
Sigma
2
  x2  x   ...   xn  x 
2
n
2
This gives us a picture of how the Standard Deviation
can tell us how an individual value relates to the bulk
of the data.
Example:
• Find the measures of central tendency and
measures of dispersion for the data below.
35, 50, 60, 60, 65, 75, 80
Xi
xi – x
( xi – x )2
35
50
60
60
65
75
80
Sum:

n

Try it…
• Find the measures of central tendency and
measure of dispersion for the data below.
42, 72, 81, 95, 98, 58, 77, 75, 83, 97, 45, 89,
93, 57, 82, 97, 52, 75
x 45,
 76
42,
52, 57, 58, 72, 75, 75, 77, 81, 82, 83, 89, 93, 95, 97, 97, 98
Median  79
Mode  75 , 97
Range  56
  17.8
Homework
• Pg. 261 #1-13odd