Transcript Section 12.1

12.1 Measures of
Central Tendency
Objectives: Find the mean, median, and mode and range
of a data set. Find or estimate the mean from a frequency
table of data.
Standards: 2.6.8A. Compare and contrast different plots
of data using values of mean, median, mode, and range.
3 commonly used measures of central tendency
are the mean, median, and mode.
HIGHEST NUMBER
MINUS
LOWEST NUMBER
RANGE = 20 – 7 = 13
Ex 1. Using the data 40, 45, 39, 40, 41, 42, 37, 41, 41, 40,
find the measures of central tendency (mean,
median, and mode), and compare them.
RANGE = 45 – 37 = 8
Ex 2. Using the data 88, 74, 98, 76, 68, 74, 89, 92,
find the measures of central tendency, and
compare them.





Mean = 82.375
Median = 82
Mode = 74
Range = 98 – 68 = 30
Mean and Median are very close, where as
the mode is lower.
Ex 4. Last month, 6 houses were sold in Souderton. The sale
prices were as follows: $140,000, $165,000, $150,000,
$300,000, $146,000, and $125,000. Find the mean, median,
and mode of the sale prices.
Explain which measure best represents the
typical sale price of a house in Souderton last month.
Mean = 171, 000
Median = 148, 000
Mode = None
Range = 175,000
Median represents the typical sale price of a house in Souderton.
II. To make a frequency table, first list each distinct
value. Then make a mark for each value in the data
set. Finally, count the number of marks to get the
respective frequency for each value, as shown below.
The number of chirps that a cricket makes is related to the
temperature. The relationship is given by the following formula
Number of chirps in 15 seconds + 40 = temp. in Fahrenheit
To verify this relationship, a class of 24 students counted cricket
chirps for 15 seconds with the following results:
*Ex 2. Make a frequency table for the data below on the
# of books read by 30 students last month. Then use
your frequency table to find the mean.
4, 0, 1, 2, 6, 0, 1, 2, 0, 4, 0, 2, 2, 1, 1,
3, 1, 0, 3, 2, 0, 1, 2, 2, 4, 1, 1, 1, 0, 4
# Books Frequency
0
1
2
3
4
5
6
Total
Product
III. When there are many different values,
a grouped frequency table is used. In a
grouped frequency table
the values are grouped into
classes that contain a
range of values.
*Ex 1. The grouped frequency table below lists the results of a survey
of 80 musicians who were asked how many hours per week
they spend practicing. Estimate the mean # of hours that
these musicians practice each week.
Hours
Class Mean
Frequency
1-5
13
6-10
9
11-15
9
16-20
14
21-25
16
26-30
8
31-35
8
36-40
3
Total
Product
*Ex 2. The grouped frequency table lists the numbers of CDs
bought by 50 students last year. Estimate the mean # of
CDs bought by these students last year.
# CDs
Class Mean
Frequency
0
4
1-5
14
6-10
9
11-15
10
16-20
8
21-25
1
26-30
2
31-35
1
36-40
1
Total
Product
Writing Activities
Review of the Measures of Central Tendency
Homework
Integrated Algebra II- Section 12.1 Level A
Honors Algebra II- Section 12.1 Level B