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```Business Math
Chapter 7:
1
7.1 Measures of Central Tendency

Find the mean
9
8

Find the median
7
6
5

Find the mode
4
3
2
1
0
2
Key Terms

Data set: a collection of values or
measurements that have a common
characteristic.

Statistic: a standardized, meaningful measure
of a set of data that reveals a certain feature or
characteristic of the data.
3
Key Terms

Mean: the arithmetic average of a set of data or
sum of the values divided by the number of
values.

Median: the middle value of a data set when
the values are arranged in order of size.

Mode: the value or values that occur most
frequently in a data set.
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7.1.1 Find the mean

Business records its daily sales. These values
are an example of a data set.
Data sets can be used to:
 Observe patterns
 Interpret information
 Make predictions about future activity
5
Find the mean of a data set.
1. Find the sum of the values.
2. Divide the sum by the total number of values.
Mean =
sum of values
number of values
6
Here’s an example.
Sales figures for the last week for the Western
region have been as follows:






Monday
\$4,200
Tuesday
\$3,980
Wednesday \$2,400
Thursday
\$3,100
Friday
\$4,600
What is the average daily sales figure?

\$3,656
7
Try these examples.

Mileage for the new salesperson has been 243,
567, 766, 422 and 352 this week. What is the
average number of miles traveled?
 470 miles daily

Prices from different suppliers of 500 sheets of
copier paper are as follows: \$3.99, \$4.75, \$3.75
and \$4.25. What is the average price?
 \$4.19
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7.1.2 Find the median.

Arrange the values in the data set from smallest
to largest (or largest to smallest) and select the
value in the middle.

If the number of values is odd, it will be exactly
in the middle.

If the number of values is even, identify the two
middle values. Add them together and divide by
two.
9
Here is an example.

A recent survey of the used car market for the particular
model John was looking for yielded several different
prices. Find the median price.

\$9,400, \$11,200, \$5,900, \$10,000, \$4,700, \$8,900,
\$7,800 and \$9,200.

Arrange from highest to lowest:
\$11,200, \$10,000, \$9,400, \$9,200, \$8,900, \$7,800,
\$5,900 and \$4,700.

Calculate the average of the two middle values.

\$9050 is the median price.
10
Try this example.

Five local moving companies quoted the following prices
to Bob’s Best Company: \$4,900, \$3800, \$2,700, \$4,400
and \$3,300. Find the median price.
 \$3,800
11
7.1.3 Find the mode.

Find the mode in a data set by counting the
number of times each value occurs.

Identify the value or values that occur most
frequently.

There may be more than one mode if the same
value occurs the same number of times as
another value.

If no one value appears more than once, there is
no mode.
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Find the mode in this data set.

Results of a placement test in mathematics
included the following scores:
65, 80, 90, 85, 95, 85, 80, 70 and 80.

Which score occurred the most frequently?

80 is the mode. It appeared three times.
13
Use the mean, median and mode.

A university recruiter is evaluating the number of
community service hours performed by ten
students who are applying for a job on campus.

Find the mean, median and mode from this data
set and determine which one or ones might help
the recruiter the most in making a realistic
assessment of the number of service hours
performed last semester.
(see next slide)
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How many hours?










Jack:
Michelle:
Bill:
Jackie:
Jason:
Larissa:
Tony:
Melanie:
Art:
Sheila:
10
14
5
2
20
12
2
18
1
0

The mode is 2.

The mean is 8.4.

The median is 7.5

Of the three values,
which one or one(s)
realistic assessment of
the number of service
hours?

Why?
15
7.2 Frequency Distributions

Make and interpret a frequency distribution.

Interpret and draw a bar graph.

Interpret and draw a line graph.

Interpret and draw a circle graph.
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7.2.1 Make and interpret a
frequency distribution.



Identify appropriate intervals for the data.
Tally the data for the intervals.
Count the number in each interval.
90
80
70
60
50
East
West
North
40
30
20
10
0
1st Qtr
2nd Qtr
3rd Qtr
4th Qtr
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Key Terms

Class intervals: special categories for grouping
the values in a data set.

Tally: a mark that is used to count data in class
intervals.

Class frequency: the number of tallies or
values in a class interval.

Grouped frequency distribution: a
compilation of class intervals, tallies, and class
frequencies of a data set.
18
7.2.2 Draw and interpret
a bar graph

Write an appropriate title.

Make appropriate labels for bars and scale. The
intervals should be equally spaced and include
the smallest and largest values.

Draw horizontal or vertical bars to represent the
data. Bars should be of uniform width.

Make additional notes as appropriate to aid
interpretation.
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Here’s an example.
Sales Volume
2001-2004
Product 3
2004
2003
2002
2001
Product 2
Product 1
0
10
20
30
40
50
Thousands of Units
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7.2.3 Interpret and draw
a line graph

Write an appropriate title.

Make and label appropriate horizontal and
vertical scales, each with equally spaced
intervals. Often, the horizontal scale represents
time.

Use points to locate data on the graph.

Connect data points with line segments or a
smooth curve.
21
Here’s an example.
Thousands of \$
First Semester Sales
100
80
60
40
20
0
Jan
Feb
Judy
Mar
Denise
Apr
May
Linda
Jun
Wally
22
7.2.4 Interpret and draw
a circle graph.

Write an appropriate title.

Find the sum of values in the data set.

Represent each value as a fraction or decimal
part of the sum of values.

For each fraction, find the number of degrees
in the sector of the circle to be represented by
the fraction or decimal. (100% = 360°)

Label each sector of the circle as appropriate.
23
Here’s an example.
Local Daycare Market Share
6%
16%
43%
Teddy Bear
La La Land
Little Gems
Other
35%
24
7.3 Measures of dispersion

Find the range.

Find the standard deviation.
From here to there...
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Key Terms

Measures of central tendency:
statistical
measurements such as the mean, median or
mode that indicate how data groups toward the
center.

Measures of variation or dispersion:
statistical measurement such as the range and
standard deviation that indicate how data is
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Key Terms

Range: the difference between the highest and
lowest values in a data set. (also called the

Deviation from the mean: the difference
between a value of a data set and the mean.

Standard variation: a statistical measurement
that shows how data is spread above and below
the mean.
27
Key Terms

Variance: a statistical measurement that is the
average of the squared deviations of data from
the mean. The square root of the variance is the
standard deviation.

Square root: the quotient of number which is
the product of that number multiplied by itself.
The square root of 81 is 9. (9 x 9 = 81)

Normal distribution: a characteristic of many
data sets that shows that data graphs into a bellshaped curve around the mean.
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7.3.1 Find the range in a data set

Find the highest and lowest values.

Find the difference between the two.

Example: The grades on the last exam were
78, 99, 87, 84, 60, 77, 80, 88, 92, and 94.
The highest value is 99.
The lowest value is 60.
The difference or the range is 39.
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7.3.2 Find the standard deviation

The deviation from the mean of a data value is
the difference between the value and the mean.

Get a clearer picture of the data set by
examining how much each data point differs or
deviates from the mean.
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Deviations from the mean

When the value is smaller than the mean, the
difference is represented by a negative
number indicating it is below or less than the
mean.

Conversely, if the value is greater than the
mean, the difference is represented by a
positive number indicating it is above or greater
than the mean.
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Find the deviation from the mean.

Find the mean of a set of data.

Mean = Sum of data values
Number of values

Find the amount that each data value deviates
or is different from the mean.

Deviation from the mean = Data value - Mean
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Here’s an example.

Data set: 38, 43, 45, 44

Mean = 42.5

First value: 38 – 42.5 =

Second value: 43 – 42.5 = 0.5 above the mean

Third value: 45 – 42.5 =
2.5 above the mean

Fourth value: 44 – 42.5 =
1.5 above the mean
-4.5 below the mean
33
Interpret the information

One value is below the mean and its deviation is
-4.5.

Three values are above the mean and the sum of
those deviations is 4.5.

The sum of all deviations from the mean is zero.
This is true of all data sets.

We have not gained any statistical insight or new
information by analyzing the sum of the
deviations from the mean.
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Average deviation

Average deviation =
Sum of deviations
Number of values
=0 =0
n
35
Find the standard deviation
of a set of data.

A statistical measure called the standard
deviation uses the square of each deviation from
the mean.

The square of a negative value is always
positive.

The squared deviations are averaged (mean)
and the result is called the variance.
36
Find the standard deviation
of a set of data.

The square root is taken of the variance so that
the result can be interpreted within the context of
the problem.

This formula averages the values by dividing by
one less than the number of values (n-1).

Several calculations are necessary and are best
organized in a table.
37
Find the standard deviation
of a set of data.
1. Find the mean.
2. Find the deviation of each value from the
mean.
3. Square each deviation.
4. Find the sum of the squared deviations.
5. Divide the sum of the squared deviations by
one less than the number of values in the data
set. This amount is called the variance.
6. Find the standard deviation by taking the
square root of the variance.
38