Returns the probability associated with a Student's t-Test.
TTEST(Data1; Data2; Mode; Type)
Data1 is the dependent array or range of data for the first record.
Data2 is the dependent array or range of data for the second record.
Mode = 1 calculates the one-tailed test, Mode = 2 the two- tailed test.
Type is the kind of t-test to perform. Type 1 means paired. Type 2 means two samples, equal variance (homoscedastic). Type 3 means two samples, unequal variance (heteroscedastic).