# [R] chisq.test using amalgamation automatically (possible ?!?)

Date: Sun 26 Jun 2005 - 20:00:15 EST

If any of observed and/or expected data has less than 5 frequencies, then chisq.test (Pearson's Chi-squared Test for Count Data from package:stats) gives warning messages. For example,

x<-c(10, 14, 10, 11, 11, 7, 8, 4, 1, 4, 4, 2, 1, 1, 2, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1)
y<-c(9.13112391745095, 13.1626482033341,

```12.6623267638188, 11.0130706413029, 9.16415925139016,
7.47441794889028, 6.03743388141852, 4.85350508692505,
3.89248001363859, 3.11803140037476, 2.49617540962629,
1.99774139023269, 1.5985926374167, 1.27909653584089,
1.02341602646530, 0.818828097315106,
0.655132353196336, 0.524159229418155,
0.418022824890164, 0.335528136508225,
0.268448671671046, 0.214779801990545,
0.171840507806838, 0.137485729582785,
```

0.109999238967747, 0.0880079144684513,
0.070413150156564)

Chi.Sq<-sum((c(x[1:7], sum(x[8:9]), sum(x[10:11]),

```sum(x[12:27]))-c(y[1:7], sum(y[8:9]), sum(y[10:11]),
sum(y[12:27])))^2/c(y[1:7], sum(y[8:9]),
sum(y[10:11]), sum(y[12:27]))) # using amalgamation
```
pchisq(Chi.Sq, df=9, ncp=0, lower.tail = FALSE, log.p = FALSE) # result being 0.8830207

but chisq.test(x,y) gives the following output with incorrect df:

Pearson's Chi-squared test

data: x and y
X-squared = 216, df = 208, p-value = 0.3373

Warning message:
Chi-squared approximation may be incorrect in: chisq.test(x, y)

Any hint, help, support, references will be highly appreciated.

Web: http://snipurl.com/ehsan
ISRT, University of Dhaka, BD