http://www.ck12.org Chapter 5. Measures of Central Tendency
5.2 Ungrouped Data to Find the Mean
Here you’ll learn how to use a frequency distribution table to calculate the mean or average of a set of ungrouped
data. You’ll also learn how to calculate the mean of a set of data using technology.
How many movies did you watch this past year? Suppose you collected data from 135 students at your school for
a year to figure how many movies each student watched. Could you come to some conclusion about the average
number of movies that an individual student might watch per year?
Watch This
First watch this video to learn about finding the mean of ungrouped data.
MEDIA
Click image to the left for more content.CK-12 Foundation: Chapter5UngroupedDatatoFindtheMeanA
Then watch this video to see some examples.
MEDIA
Click image to the left for more content.CK-12 Foundation: Chapter5UngroupedDatatoFindtheMeanB
Guidance
When a data set is large, afrequency distribution tableis often used to display the data in an organized way. A
frequency distribution table lists the data values, as well as the number of times each value appears in the data set.
A frequency distribution table is easy to both read and interpret and in this concept is used forungrouped data, or
data that is listed.
The numbers in a frequency distribution table do not have to be put in order. To make it easier to enter the values
in the table, a tally column is often inserted. Inserting a tally column allows you to account for every value in the
data set, without having to continually scan the numbers to find them in the list. A slash (/) is used to represent the
presence of a value in the list, and the total number of slashes will be the frequency. If a tally column is inserted, the
table will consist of 3 columns, and if no tally column is inserted, the table will consist of 2 columns. The formula
that was written to determine the mean,x=∑x^1 +x^2 +nx^3 +...+xn, does not show any multiplication of the numbers by
their frequencies. However, this can be easily inserted into this formula as shown below:
x=
∑x 1 f 1 +x 2 f 2 +x 3 f 3 +...+xnfn
f 1 +f 2 +f 3 +...+fn