The Importance of Histograms and Descriptive Statistics
The word “statistics” comes from the German word “stadt”. Stadt means “city” but in the 18th century each city was a state in its own right. And the people who ran those states needed to have the facts. What is the population? What is the food production? How many men are available for the military? What is the birth rate? Information about the state came to be known as Statistics. In today’s complex world people do data mining, gather big data, and perform tests of statistical hypotheses. It is easy to forget that one of the primary tasks of statistics is purely descriptive.
Creating Frequency Distributions and Histograms in Excel 2011 Instructions for Mac Users Frequency Distributions 1. Create a new spreadsheet with the numeric variable you want to make a frequency distribution for. Sort the variable ascending by going to Data! Sort and selecting the appropriate column. Histogram with relative frequency. I have a nice histogram that shows, on the vertical axis, the frequency per bin. That is, the absolute number of data points per bin. I want to change that to relative frequency, so it shows the percent, or portion, of the total, per bin. Instead of the vertical axis showing, say, 50 data points in a bin, I.
Calculating descriptive statistics such as mean, median, and variance is easy, since Excel has functions for this purpose. Let’s look at something a little more complicated but a necessary tool in the statistician’s toolbox, the frequency distribution and its graphical comrade, the histogram.
Creating a Histogram using Microsoft Excel
We’ll stick with the centuries-old tradition and gather some information about cities, starting with a table of income information about cities in the United States from the year 2009. We would like to observe the frequency distribution of median family incomes. The Excel data analysis toolpak has a nice dialog box for doing this automatically, but we’re going to take charge and do it ourselves using the FREQUENCY function.
We must first define the bins, which is to say the value ranges into which our data will be sorted. Generally this is done in a worksheet column, and Excel’s auto-fill feature makes this easy. In this example we will create bins from 10,000 to 170,0000 at increments of 5000.
Now we are ready to tabulate our frequency distribution. We highlight a second column next to our column of bin values. In the formula bar, we enter =FREQUENCY(. The first argument is the range containing our data. If you enter this range by highlighting it on the worksheet, be careful not to include the column heading. Only the data is highlighted. The second argument to FREQUENCY is the range containing the bin values. After entering the range in the formula bar close the parenthesis, but
Do not hit enter!
Highlight the range where the frequency results will appear and enter the frequency function.
Enter both the data ranges and the frequency bin range.
You’re almost ready but
Do not hit enter yet!
FREQUENCY if one of the many valuable Excel array functions. Mr. Excel calls them “CSE” functions, and this name is well chosen. The CSE acronym reminds us that you enter array functions not by hitting enter but by hitting <ctrl><shift><enter>. When you hit control-shift-enter, the formua will be entered in the highlighted cells. Note that in the formula bar, the function is now within curly braces. You cannot just type in these curly braces yourself. You must let Excel enter them after you type <ctrl><shift><enter>.
Now that we have our frequency distribution, it is impossible to resist creating a chart. The frequency range is already highlighted; we have only to click on “column chart” from Excel’s Insert ribbon tab. The chart looks OK, but we see that we will have to edit the horizontal axis label to reflect our frequency bins. We can right-click on the chart and choose “Select Data…” . Click the “Edit” button on the right-hand side, the side for the horizontal axis labels. Then enter the range containing the frequency bins.
Right-click the chart and choose “Select Data…” to edit the axis labels.
Right-click the chart and choose “Select Data…” to edit the axis labels.
After entering a title and choosing a style, we have our finished frequency histogram!
I hope you enjoyed my first Excel post! Stay tuned for my next one where we cover Standard Deviations.
1. Create a column for your independent variables (your x-values). For example, if you are comparing the performance of salespersons, write 'Jim' in cell A2, 'John' in cell A3, 'Sue' in cell A4, 'Pat' in cell A5 and Joe in cell 'A6.'2. Create a column with your dependent variables (your y-values). For the example given in Step 1, write 12 in cell B2,11 in cell B3,10 in cell B4, 9 in cell B5 and 4 in cell B6.
3. Sum the dependent variable column by clicking an empty cell at the bottom of the data and entering the summation formula. For the Step 1 example, you have information in cells B2 to B6, so the formula is =SUM(B2:B6).
4. Create a second set of y-values by calculating the percentage of sales for each item. Use a formula to calculate this for you; for the example given in the steps above, enter =B2/B7 in cell C2, =B3/B7 in cell C3, =B4/B7 in cell C4, and =B5/B7 in cell C5.
Excel For Mac Relative Frequency Histogram Function
