Standard Deviation (SD) and InterQuartile Range (IQR) Investigate Six Example Data Sets from the DASL project  Take the Quiz The Investigations: Load each of the six sets of data. Click Sort to order the data values. Compare the standard deviation and the IQR for each data set. Both are measures of how spread out the data values are. An outlier is a data value more than 1.5 * IQR above the third quartile, or more than 1.5 * IQR below the first quartile. What are the outliers in the six example data sets?  Data sets with fewer than 40 observations, and which contain outliers, are not data sets appropriate for  t-tests or confidence intervals. Are there any such data sets among these six example data sets? What percent of data values in each sample data set are within two standard deviations of the mean? Highlight then delete the highest value from a data set. Replace it with a value 10 times greater than the original. Press Sort, then check the standard deviation  and IQR again.

Highlight then delete the lowest value from a data set. Replace it with a value 1/10 of the original. Press Sort, then check the standard deviation and IQR again.	Load a small set of data values  (or click Clear and replace them with some of your own). Note the standard deviation and the IQR. Now add 5 to each data value.  Check the standard deviation and the IQR again. How did they change?	Load a small set of data values  (or click Clear and replace them with some of your own). Note the standard deviation and the IQR. Now double each data value.  Check the standard deviation and the IQR again. How did they change?
	Click Clear and enter 10 data values which are all the same. Check the standard deviation and the IQR.

 

You've done the Investigations, now try the  QUIZ!