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.