ALT #2: Measures of Variability

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Overview

The standard deviation is a measure with which many people struggle. This ALT uses an intuitive approach to help you understand why the standard deviation is often one of the most important of all statistical measures. In this ALT, you use the mean, median, mode, range, and standard deviation to interpret data.

After completing this ALT, you should be able to demonstrate the following competencies:

• Collect, process, and display data so that usable information is represented (Comp. 1).
• Prepare basic charts and graphs (Comp. 2).
• Make inferences based on data analysis
  (Comp. 3).
• Apply measure of central tendency and variability (Comp. 4).
• Describe in general terms the normal curve and use its properties to make conjectures about sets of data that are normally distributed (Comp. 6).

Materials and Equipment
1 graphing calculator, such as model TI-82, TI-85, or TI-86

Safety and Disposal
No special safety or disposal procedures are required.

Pre-Activity

As we mentioned earlier, there are a large number of measurements that you can make on any given data set. Most of these measurements measure one of two characteristics: the central tendency of the data or its variability. A measurement of the variability will measure how much the data is spread out.

Being able to measure the variability of data will prove to be a very powerful tool. In ALT #2, we will consider two measures of variability: the range and standard deviation. We will also talk about what it means for a data set to be normally distributed.

In addition, applying these measures to data that is normally distributed will allow us to do such things as statistical process control (SPC), a very important topic for any industry wanting to produce quality products.

To prepare for the activity:

• Read Information Sheet: Measures of Variability in your Basic Statistical Variation Participant Journal.
• Read more about standard deviation.
• Read about Data Analysis Using MS Excel.

Activity

In your team, perform the following steps to complete the activity:

1. Complete Data Sheet: Measures of Variability and Data Sheet: Reviewing Measures of Variability.

Your team should now post all of its results recorded on Data Sheet: Measures of Variability and Data Sheet: Reviewing Measures of Variability to the discussion board.

Assignment
To prepare for ALT #3: The Coin Toss, read Information Sheet: Frequency Charts and Histograms in your Basic Statistical Variation Participant Journal.

Assessment
Your facilitator may use Assessment Sheet: Measures of Variability from your Basic Statistical Variation Participant Journal to evaluate your results from the activity and your posting to the Discussion Board.

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