Data Matters with Excel®

Activity 1.2

The project in Section 1.2 requires these steps.

1. Use the random number generator to create random observations. When you are done, each cell will have a single number produced by the random number generator.
2. Look at the first 20 random numbers. There should be no sequences in them that you can see. Most random number generators have a way to produce random decimals between 0 and 1 for which every decimal is equally likely and shows up an equal number of times. Figure out how to get this kind of random number in your software.
3. Repeat these steps to see how the random number generator produces new random numbers.
4. Figure out what the chances are that the random number generator will produce a number less than .5. (This may be tough, and I strongly recommend you ask friends for help in thinking this through.) Write down your answer and how you figured it out.

You will put your random variables in the first column. To name the column, select the top-leftmost cell and type Random Number.

Using your keyboard arrows, move down to the cell directly below. Type =RAND() into the cell and press “Enter.” The function RAND() produces the kind of random numbers we are looking for: digits from 0 to 1 for which every digit is equally likely.

To get the first 20 random numbers, put the same equation in cells below. Select the cell you just put the equation in. The cell gets a thicker black border. In the lower right of the cell is a small square. Click on that square and drag it down. That copies the equation into whichever cells are included within the thicker black border.

Name your second column Under .5.

In the cell directly underneath, type = (an equal sign), select the random number just next to the cell you’re working in, type <.5 , then press “Enter.” You will get a FALSE or TRUE, depending on whether the random number in the first column is less than .5.

Select the cell you just entered the equation in, to get the thick border. Click on the little square and drag down to fill the column with the equation.

Get the proportions for this new column (Data, PivotTable and PivotChart Report, and so on).

Once you have your PivotChart, you have only to click on the red exclamation point on the PivotChart menu to replace the random numbers with new random numbers.

As you think about the problem, it might help to keep in mind that when you use =RAND(), every decimal from 0 to 1 is equally likely.

It also might help to have more observations. Repeat the steps, dragging the equations further down. You will have to re-create your PivotChart to get it to use all of the new rows.

Check how the additional cases affect the proportion of random numbers under .5 that appear.