# Module on measures of variability

Please be sure to download the z-score chart by clicking this link. The Range The range is the difference between the highest and lowest scores in a data set and is the simplest measure of spread. The mean, often shown as an x or a y variable with a line over it pronounced either "x-bar" or "y-bar"is the sum of all the scores divided by the total number of scores.

The video was produced by YouTube user, Jeremy Jones. Formulae for the standard deviation Whilst it is not necessary to learn the formula for calculating the standard deviation, there may be times when you wish to include it in a report or dissertation.

I added the values to get a sum of In this course, we will be going over four measures of variability: You are interested in determining which pricing method has less variability so you sample several of each and calculate the mean and standard deviation for the sampled items that are priced per roll, and the mean and standard deviation for the sampled items that are priced per sheet.

You should also utilize the homework problems and the Suggested Additional Practice below to practice calculating the measures of variation either by hand or with Google. Therefore the range is 6. Note that finding the median requires first ordering all of the observations from least to greatest.

Quiz 1 Quiz 2 Figure 1. Therefore, the column "Deviation from Mean" contains the score minus 7. Unlike the median, however, the mean is sensitive to outliers. Summary The range, inter-quartile range and standard deviation are all measures that indicate the amount of variability within a dataset.

It is important to remember that one has to use the formula: It is the most robust and widely used measure of dispersion since, unlike the range and inter-quartile range, it takes into account every variable in the dataset.

Variance is the average squared distance from the mean.

These graphs represent the scores on two quizzes. We calculated the variance to be 2 and the standard deviation to be 1. Variance and Standard Deviation Two vending machines A and B drop candies when a quarter is inserted.

Determine the relative variability of two distributions Compute the range Compute the variance in the population Estimate the variance from a sample Compute the standard deviation from the variance What is Variability? The variance would be in squared units, for example inches2. The standard deviation is the most robust measure of variability since it takes into account a measure of how every value in the dataset varies from the mean.

Comparing Prices You are shopping for toilet tissue. Stripping the Dread from the Data Various measures of the dispersion (or variation) are available, the most common being the range, quartile deviation or semiinter quartile range, percentile, decile, and standard deviation.

Range The range refers to the difference between. Next - Grade 6 Mathematics Module 6, Topic B, Lesson 9. Grade 6 Mathematics Module 6, Topic B, Lesson 8 Students compare and contrast two small data sets that have the same mean but different amounts of variability.

Recognize that a measure of center for a numerical data set summarizes all of its values with a. Variability can also be defined in terms of how close the scores in the distribution are to the middle of the distribution.

Using the mean as the measure of the middle of the distribution, the variance is defined as the average squared difference of. Measures of variability: the range, inter-quartile range and standard deviation There are many ways of describing the variability in some data set.

In this guide we discuss the range, interquartile range and standard deviation.

Looking specifically at range, variance, and standard deviation, this lesson explores the relationship between these measures and samples.

Measures of Variability Think about the following, then click on the icon to the left to display the statistical answer.

If you can use two numbers to summarize Jessica's weight data, which two characteristics will you use as measures?

Module on measures of variability
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