Better instructions will be placed here at a later date. For now, here are some from the Excel Help menu.

t-test

Returns the probability associated with a Student's t-Test. Use TTEST to determine whether two samples are likely to have come from the same two underlying populations that have the same mean.

Syntax

TTEST(array1, array2, tails, type)

• Array1 is the first data set.
• Array2 is the second data set.
• Tails specifies the number of distribution tails. If tails = 1, TTEST uses the one-tailed distribution. If tails = 2, TTEST uses the two-tailed distribution.
• Type is the kind of t-test to perform.
  1 - Paired
  2 - Two-sample equal variance (homoscedastic)
  3 - Two-sample unequal variance (heteroscedastic)

Remarks

• If array1 and array2 have a different number of data points, and type = 1 (paired), TTEST returns the #N/A error value.
• The tails and type arguments are truncated to integers.
• If tails or type is non-numeric, TTEST returns the #VALUE! error value.
• If tails is any value other than 1 or 2, TTEST returns the #NUM! error value.

Example

TTEST({3,4,5,8,9,1,2,4,5},{6,19,3,2,14,4,5,17,1},2,1) equals 0.196016