208 Fundamentals of Statistics
Excel creates 16 columns each containing 100 rows of random values
from a standard normal distribution. Now take the average of each row; this
provides you with 100 rows of sample averages with each average drawn
from a sample of 16 random normal values.To calculate the averages of the 1,000 random samples:1 Click cell Q1, type the formula 5 average(A1:P1), and press Enter.
2 Click cell Q1 again and drag the fi ll handle down to cover the range
Q1:Q100. Column Q now contains the average of each of the 100
samples on the worksheet.The column of averages you just created should be much less variable
than each of the individual samples, because the average smoothes out the
highs and the lows of the values found within each sample. What kind of
distribution does it have? Let’s investigate by creating a histogram of the
sample averages.To create a histogram of the sample averages:1 Click Single Variable Charts from the StatPlus menu and then click
Histograms.
2 Click the Data Values button, click the Use Range References option
button, and select the range P1:P100. Deselect the Range Includes
Row of Column Labels checkbox. Click the OK button.
3 Click the Normal Curve checkbox.
4 Click the Output button and save the histogram to a chart sheet
named Sample Average Histogram.
5 Click the OK button to start creating the histogram.
Figure 5-21 shows the resulting histogram (yours will differ since it
comes from a different random sample).