1. 15.3 Measures of Central Tendency

2. *set of data can have one mode, no mode, or more than one mode
Common “averages” for data sets – called “measures of central tendency”
arithmetic
Mean  numerical average
Median  middle value in ranked data
Mode  most occurring value
*set of data can have one mode, no mode, or more than one mode
Ex 1) The low temperatures in degrees Fahrenheit for 15 days in March in Omaha, NE were 5, 9, 11, 2, 7, 1, 4, 9, 10, 4, 2, 2, 8, 5, 3.
Rank data: 1, 2, 2, 2, 3, 4, 4, 5, 5, 7, 8, 9, 9, 10, 11
a) mean
b) median  8th item = 5
c) mode = 2

3. Thought Questions
Ex 2) How does an extreme value affect the mean?
For instance in Ex 1, replace 11 with 20 or 35.
Discuss with a friend.
Ex 3) Describe an instance when each of the 3 “measures of central tendency” would be the best to illustrate the “average” for a data set.

4. *If numbers are presented in a frequency distribution, median & mode are very easy to find.
Ex 4) Attendance of a company’s board members at the last 20 meetings has been recorded.
Number present 11 12 13 14 15 16
Frequency 1 2 6 7 3
Mode = 15
Median = with 20 values, it’s average of 10th & 11th term
Mean =

5. Homework
# Pg #3 – 9, 11 – 16, 18 – 20, 26 – 29, 32 – 35