Microsoft Office Tutorials and References
In Depth Information
Testing to the T
Use TTEST to determine the probability that two samples come from the same
Here’s how to use the TTEST function:
1. Enter two sets of data.
2. Position the cursor in the cell where you want the result to appear.
3. Enter =TTEST( to start the function.
4. Drag the pointer over the first list, or enter the address of its range.
5. Enter a comma ( ,).
6. Drag the pointer over the second list, or enter the address of its range.
7. Enter a comma ( ,).
8. Enter a 1 for a one-tailed test, or enter a 2 for a two-tailed test.
9. Enter a comma ( ,).
10. Enter one of the following:
•1 for a for a paired test
11. Enter a ).
If you ever took a statistics course, you may recall that a t-test returns a
t-value, which you then had to look up in a table to determine the associated
probability. Excel’s TTEST function combines these two steps. It calculates
the t-value internally and determines the probability. You never see the actual
t-value, just the probability — which is what you’re interested in anyway!
The TDIST function returns the probability for a given t-value and degrees
of freedom. You would use this function if you had a calculated t-value and
wanted to determine the associated probability. Note that the TTEST
function doesn’t return a t-value but rather a probability, so you wouldn’t use
TDIST with the result that is returned by TTEST. Instead, you would use
TDIST if you had one or more t-values calculated elsewhere and needed to
determine the associated probabilities.
TDIST takes three arguments:
✓ The t-value
✓ The degrees of freedom
✓ The number of tails (1 or 2)