Lesson 2

Visual displays of data are useful because they quickly reveal information about the data set. Another way to meaningfully describe a set of data is to use a summary statistic. For instance, you and your group may have used measures of central tendency to summarize the quiz marks. You might have calculated the mean, median, and mode of the data sets. Or you may have calculated measures of dispersion, such as range.

 

Each one of these summary statistics is a tool that provides specific information about the data. This information can be very useful for comparing sets of data.

 

For instance, summary statistics for Mr. Kong’s statistics quiz show the following:

• The Block 1 class had a higher mean.

• The most common score in both classes was 7 out of 10.

• The spread of marks (i.e., range) was greater in Block 4 than in Block 1.

Statistics Quiz Block 1
number of quizzes	30
mean	7.1
mode	7
median	7.5
range	5

Statistics Quiz Block 4
number of quizzes	25
mean	6.5
mode	7
median	7
range	6.5

Another measure of dispersion is standard deviation. Standard deviation gives information on the spread or the amount of dispersion in the data set. Basically, it shows how much dispersion or variation there is from the mean (i.e., average). The standard deviation can be low or high depending on how spread out the data is.

 

Try This 1

 

You should place your completed Try This activities in your course folder. Your teacher may ask to see your completed Try This activities. For more information on Try This activities, refer to the Course Introduction.

 

Use the applet Standard Deviation to determine what happens to data distribution as you increase the standard deviation.