How to Do the Calculations for One Sample t-Test Using Statlets (Like Problem # 4 of the Module 2 Essay Exam)

For this tutorial, let's test to see if the average birth weights of infant born in our hospital is less than 3100 grams.

1. When you start Statlets, the following spreadsheet should appear. If not, click on the "File" pull down window and select "New."

2. Click on "Col_1" and the entire row should become shaded.

3. Type a new variable name, let's use "Weight" then press return: Then enter the following numbers, pressing return after each one:

2973

3193

2990

3077

3092

2996

2954

3006

3106

3077

These are the birth weights (in grams) of a random sample of infants born in the hospital.

4. Click on the "Analyze" menu, slide down to "One Sample" and slip over to "One Variable Analysis."

the following dialog box will appear:

5. Click on "Weight" then click on arrowhead that is pointing away from Weight.

6. Click on the "t-test" tab and the following should appear.

The default is a two tailed test, that tests the alternative hypothesis that the mean is different than 0 at an alpha level of .05.

7. Because our hypothesis differs from the default, click on the [Options] button.

Change the "Null hypothesis:" from 0.0 to 3100, move the radio button to "Less than," but leave the "Alpha:" at 5.0%.

Then press the [OK] button.

From this output, we would make the following decision and conclusion:

Decision: Reject H0

Conclusion: At an alpha level of .05, the birth weights of neonates born in our hospital is significantly less than 3100, t(9) = -2.27, p = .0248.

8. Now we want to save this output by either printing it or doing a screen capture.

To print, click on the "File" pull-down menu and select "Print." The following dialog box will appear.

Make sure that the radio button for "Current tab only" is selected as shown above, then press the "OK" button.

Instead of printing, or in addition to it, you can do a screen capture and then paste the screen image into a document. To do a screen capture, hold down the "Alt" key as you press the "Print Screen" key. This puts the active window (your results) in your computer's clipboard. Now, without closing Statlet, open your word processor (Word, Works, WordPerfect, etc) and do a paste (either Edit/Paste or hold down the "Ctrl" key as you press the "v" key). All the images in this tutorial were done using this method of screen capturing. Note: if you press the "Print Screen" key without pressing the "Alt" button, you will capture the entire screen and not just the active window (which is all we need to capture) for our purposes.