Difference between revisions of "Documentation/How Tos/Calc: FTEST function"
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FTEST
Returns the result of an Ftest.
Syntax:
FTEST(data1; data2)
 data1 and data2 are ranges or arrays (possibly of different size) containing numbers, on which the Ftest is performed. The Ftest calculates the likelihood that two samples have the same variance.
 In effect, the sample variances of data1 and data2 are calculated. data1 and data2 are reordered if necessary so that data1 has the larger variance (σ_{1}) and data2 the smaller (σ_{2}), and an F_value is calculated as σ_{1}/σ_{2}. The result returned by FTEST is 2*FDIST(F_value; COUNT(data1)1; COUNT(data2)1). This is the twotailed probability that the variances in data1 and data2 are not significantly different. (The internal algorithms used by Calc are more sophisticated than this).
 Advanced topic:
 The parameters data1 and data2 are always evaluated as array formulas.
Example:
FTEST({9;8;6;8}; {5;6;7})
 returns approximately 0.82. The probability that the variances of these two samples are not significantly different is about 82%. Note: a real world example would need more data than this.
Issues:
 Earlier versions of Excel and the ODFF draft specification incorrectly claimed this was a onetailed test.