StatTutor: College Drinking (Question 1)
Description of activity and Excel instructions: StatTutor College Drinking (Question 1)
Dataset: Direct link for drinking.xls not available.
Contents
Calculate descriptive statistics
Before beginning on the table of descriptive statistics, let's sort the data to make it easier to check the tabulation.
- To select the whole worksheet, type the key combination Ctrl+A.
- Select Data > Sort....
The Sort dialog displays.
- In the Sort Criteria tab, select Column B (the Alcohol variable) in the drop down menu under Sort by.
- Click the Options tab.
- Check the box next to Range contains column labels.
- Click OK.
The "O"' values are listed at the top and the missing values "*" are listed at the bottom.
Now let's make the row and column labels for the table.
- Select a cell to be the upper left corner of the table; choose a cell in an empty section of your worksheet (to the right of the data columns)
- Type "Statistic".
- In the each successive cell under Statistic, type "Mean", "Stand Dev", "Min", "Q1", "Median", "Q3", "Max".
- In the cell to the right of Statistic, type "Alcohol".
Now let's add the formulas. We use [range] to indicate where the cell range should go. When you enter the range of data, be sure to exclude the cells with an asterisk (*) that indicate missing values. Enter the formulas in the cell to the right of each statistic's label.
- Mean: Type "=average([range])".
- Stand Dev: Type "=stdev([range])".
- Q1: Type "=quartile([range], 1)".
- Min: Type "=min([range])".
- Median: Type "=median([range])".
- Max: Type "=max([range])".
- Q3: Type "=quartile([range], 3)".
Create the frequency table
First we need to define the bins (also called intervals or classes) in which to group the data.
- Decide on an appropriate bin width, and then in one of the columns to the right of the data, make a list of the upper limit in each bin, from lowest down to highest. For example, if the data range from 3 to 86, you might choose a bin width of 10. Your bins would start at 10, then 20, 30,..., 90). In general, choose a bin width so that there are between 5 and 15 bins. And, remember the bin number is the upper limit of the bin, so there will be no bin labeled "0".
In an effort to create better x-axis labels for the histgram, let's create data labels in the column to the right of the bins.
- Highlight the block of cells.
- Select Format > Cells....
The Format Cells dialog displays.
- Select the Numbers tab.
- Select Text in the dropdown box under Category.
- Click OK.
- Enter the range in each cell (for example, '0-5' instead of just '5').
Now add the frequencies in the next column to the right.
- Use the FREQUENCY function to calculate the number of observations in each bin. Display the frequency data in the cells to the right of the bin labels. Remember that the FREQUENCY function requires two arguments: data and classes. Indicate the correct range for each of these.
Create the histogram
- Choose Insert > Chart....
The Chart Wizard dialog box opens.
- On 1. Chart Type: select Column.
- On 2. Data Range: insert the data range (labels and frequencies, but not the upper limit in each bin), and indicate that the data series is in a column, and the first column is a label.
No revisions are necessary on 3. Data Series.
- On 4. Chart Elements: enter a title, axis labels, and adjust other elements on the chart.
- Click Finish.
The chart will be inserted into the open sheet. Widen the chart as needed to correctly display the x-axis labels.
- Move the chart to be situated next to the frequency data.
- Remove the space between the bars, using the Object Properties... option.
- Click OK.
Report results
The next step in the StatTutor exercise for Question 1 is to Report Results. The exercise asks you to
Describe the key features of data display and support your description with numerical measures.
Enter your description in BOTH the box provided in the StatTutor exercise AND next to your data analysis for Question 1 in YOUR spreadsheet. Tip: merge a block of cells to create a space on the sheet for your results write-up.
Draw conclusions
Following the Report Results page is the Draw Conclusions section. The Consider what the results mean section asks
What do the results you got indicate about the typical number of alcoholic beverages as student drinks per week? Do your results suggest that drinking is a problem at this university?
Enter your response in BOTH the box provided in the StatTutor exercise AND below your description of results for Question 1 in YOUR spreadsheet.