Excel:
=CHIDIST(x, degrees of freedom)
x = a value of the chi-square statistic
df = degrees of freedom
Result: Area in the tail to the right of that value
That is, you've computed a Test Statistic and you want the p-value.
Example: When df = 20, what about chi-square value 31.4 ?
0.050126 =CHIDIST(31.4,20)
Interpretation: 0.0501 of the area is to the right, 0.9499 is to the left
=CHIINV(probability, degrees of freedom)
probability = area in the right tail
df = degrees of freedom
Result: chi-square value
Example: [JK10 Page 518]
When df = 20, what chi-square value divides the area into 95% left, 5% right?
31.41043 =CHIINV(0.05,20)
Example: [JK10 Page 518]
When df =14, what chi-square value divides the area into 10% left, 90% right?
7.789534 =CHIINV(1-0.1,14)
Example: When df = 14, what chi-square value is the median?
13.33927 =CHIINV(0.5,14)
When df =14, what chi-square value divides the area into 90% left, 10% right?
21.06414 =CHIINV(0.1,14)
TI-84
In 2ND DISTR, there are two functions for the χ2 distribution.
2
If you have a χ2 Test Statistic and you want to find the p-value, use 8:χ cdf(
Example: When df = 20, what about chi-square value 31.4 ?
Left bound
31.4
Right bound
1E99
Degrees of freedom
20
There is no inverse version of this function on the TI-84 !
2
2
If you want to graph a χ distribution, use 7:χ pdf(