2.5 Measure of Central Tendency

Central Tendency

• We are constantly trying to “figure stuff out” about sets of data.

• Does the data crowd up around certain areas?

Mean

Average of population= mew =

Median

• Simply the middle number

• Arrange in order and find middle term, if there are 2 middles, average them.

Mode

• Most common occurrence of a number.

Outlier

• Data points that lay well outside the majority of the data.

Compare

• Determine Mean, Median, and Mode.Class 1

Class 2

45 51 55 64 66 70 71 71 71 7382 83 84 90 95

12 15 44 50 54 61 61 63 69 7374 75 80 80 81 84 91 92

Observations?

Class A Class B

Mode 71 61, 80

Median 71 71

Mean 71.4 64.4

Grouped Data

Find Median and Mode

Age of Car Owners

Frequency

16-20 1021-25 1826-30 1231-35 836-40 2

Find Median

Age of Car Owners

Midpoint Frequency fixi

16-20 10

21-25 18

26-30 12

31-35 8

36-40 2

Weighted Mean

Example

• Personnel Manager at Google inc. considers 5 criteria when interviewing a job applicant. The manager gave each applicant a score between 1 and 5 and weights each category according to importance.

Criterion Score (xi) Weighting Factor (wi)

x* w

Education 4 2Job Experience 2 2 Interpersonal Skills

5 3

Communication Skills

5 4

References 4 1

Find Weighted Average

Assignment

• Pg 133 #’s 1,2,8,9,11ab