• Describe the differences in variability in histograms and dotplots. 
• Calculate and describe standard deviation.

Standard Deviation

Now, let’s explore the impact of extreme values, or outliers, on the variability of the G-rated movies.

As determined in the previous questions, there is a single data point that is an outlier for this data set: The one G-rated movie that has a runtime of [latex]357[/latex] minutes!

Step 1: Select the Several Groups tab.

Step 2: Locate the drop-down menu under Enter Data and select From Textbook.

Step 3: Locate the drop-down menu under Data Set and select Movie Run Time.

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Let’s remove the outlier from the statistical calculations and graphs.

Step 1: Go to the list of G-rated movie run times
Step 2: Locate, select, and remove (delete) the point [latex]357[/latex] from the list. The Descriptive Statistics section will automatically update based on your new data set that excludes the outlier.

The standard deviation will always include all data values from the data set. We may remove an outlier and recalculate to see the effect of the outlier on the measures of center and spread, but these do not reflect the true mean and standard deviation for the data set.