In the following article, The Median Isn't The Message, Stephen Jay Gould tells a personal story in which knowledge of statistics had a crucial influence in his life.

An excellent example of a skewed distribution is provided in the following histogram of baseball salaries. The mean salary is $1,183,416; the median is $500,000. For symmetric distributions, the mean and median are equal. The further your data are from being symmetric, the more distance there is between the mean and the median. To get a feel for why this is so, try out this Interactive Numberline.

Read the instructions there and see for yourself how the two measures work. Note that you enter this page in the middle....at the beginning of the page there are some definitions and helpful tips on using Minitab.

Demo: Calculations

Want to see how to calculate the Variance and Standard Deviation? This site has a text-based animation that shows the calculations. Be patient--it goes through the calculations slowly so you can see exactly how it works. The animation repeats, so if you miss something, you get a chance to see it again.

Review

View this slide show to review Summary Statistics. The controls to go forward or backward appear at the top of the window.

Interacting with Statistics

The following data show the number of bombing incidents from 1990 (the first row) to 1995 (the last row). Highlight the following numbers with your mouse and copy (choose the 'copy' selection from your browser's Edit menu).

1582

2499

2989

2980

3163

2577

You'll need it at this site, where you'll get to Compute the Median. Move your mouse over the box asking you to type in your data and click. You can choose 'Paste' from your browser's Edit menu to paste the data in the box. Then click on 'Find the Median of These' to calculate the median.
If you're interested in this data, you can get more of it at the FBI Bombing Statistics Site. See the References section for more information

Make a boxplot of the same data. When you get to this site the text asks you to submit parameters. Just click on the button that says 'submit' and then you'll get to the page that asks for your data. Paste the data table in the data box and click on 'Send Me'.

Assignment Getting Help with Your Computations:

1. Use the following data to make a boxplot. At this location, you can make multiple boxplots on a single page. The data given are the number of explosive bombings (first half, labeled with '1') and incendiary bombings (second half, labeled with a '2') for the years 1990 to 1995.

   931	1
   1551	1
   1911	1
   1880	1
   1916	1
   1562	1
   267	2
   423	2
   582	2
   538	2
   545	2
   406	2

   
   As you did in the previous boxplot exercise, highlight and copy the above data and use it to Make Multiple Boxplots.

2. Review the exercise that you experimented with from the last chapter:
   The Histogram Explorer. Now that you're much more familiar with distributions and measures of central tendency, the interactive demo will be more meaningful.