Microsoft Office Tutorials and References
In Depth Information
CHIDIST
CHIDIST
CHIDIST returns the one-tailed probability of the chi-squared ( X 2 ) distribution; the area in the
right tail under the chi-squared distribution cur ve.
=CHIDIST(x,degrees_freedom)
The CHIDIST function is used in conjunction with the CHITEST function to perform
hypothesis tests, including: experiments with more than two categories (goodness-of-fit tests or
multinomial experiments ); contingency tables (independence and homogeneity tests); and
variance and standard deviation of a single population.
For example, an experiment might hypothesize that farmers who do not till the soil before
planting a crop, will yield a larger har vest. By comparing the obser ved results with the
expected ones, you can decide whether the hypothesis is valid.
X Is the value at which you want to evaluate the distribution.
DEGREES FREEDOM The degrees of freedom are typically the number of obser vations
that can be chosen freely and is usually denoted by df.
Small degrees of freedom skew the distribution cur ve to the right. Large degrees of freedom
skew the distribution cur ve to the left, making it more symmetrical like a normal distribution
(bell-shaped cur ve). Figure 11.4 shows the results of several CHIDIST calculations using
different values of X and degrees of freedom.
Figure 11.4
If the CHITEST result
is more than the
CHIDIST result, the
hypothesis is typically
rejected.
CHIINV
CHIINV returns the inverse of the one-tailed probability of the chi-squared ( x 2 ) distribution.
=CHIINV(probability,degrees_freedom)
Where the CHIDIST returns the area under the right tail of the distribution cur ve, the CHIINV
returns the remaining area under the distribution cur ve. The total area is 1.
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