For Professor Ryan ONLY

Statistics for Business and Economics, Ch. 9

· Chi Square The thread has 4 unread messages.

created by LOUIS DAILY

Last updated Feb 25, 2015, 9:05 PM

4

· Comment on Feb 22, 2015, 10:48 PM

Message collapsed. Message unread Chi Square

posted by LOUIS DAILY at Feb 22, 2015, 10:48 PM

Last updated Feb 22, 2015, 10:48 PM

Chi Square is used with nominal or frequency data.  Chi Square compares the observed frequencies with the expected frequencies.   There are two kinds of Chi Square tests:  a goodness of fit test, and a test of independence.

 

Discussion.  Questions?

· Comment on Feb 25, 2015, 12:49 PM

Message collapsed. Message unread Re: Chi Square

posted by PATRICIA MARCUS at Feb 25, 2015, 12:49 PM

Last updated Feb 25, 2015, 12:49 PM

·

The chi in chi-square is the Greek letter χ, pronounced ki as in kite. Chi-square (χ2) procedures measures the differences between observed (O) and expected (E) frequencies of nominal variables, in which subjects are grouped in categories or cells. There are two basic types of chi-square analysis, the Goodness of Fit Test, used with a single nominal variable, and the Test of Independence, used with two nominal variables. Both types of chi-square use the same formula. Computing the Chi Square. The first step is to subtract expected frequencies (E) from the observed (O). These

differences fall under the "O-E" column. Notice that Σ(O-E)=0, just as Σx=0. The second step is to square the differences. These squares are found under the "(O-E)2" column. The third step is to divide the squared differences by the expected values.

· Comment on Feb 25, 2015, 6:42 PM

Message collapsed. Message unread Re: Chi Square

posted by JUDEENE WALKER at Feb 25, 2015, 6:42 PM

Last updated Feb 25, 2015, 6:42 PM

·

HI professor I have heard of the "Chi Square" until I started this course; after reading your post and other resources I am more clear on the chi square and it uses.  I learned that the Chi square test is used to determine whether there is a significant difference between the expected frequencies and the observed frequencies in one or more categories. In a more simple terms (the Chi Square test is used  if test if s a sample of data came from a population with  a specific distribution) Snedecor & Cochran 1989.

The goodness of fit test and the test of independence are two kinds of Chi Square tests; the goodness of fit test can be applied to any distribution (Binomial and Poisson) for which we can calculate the cumulative distribution function. 

On the other hand the test of independence is applied when we have two categorical variables from a single population. It is often used to determine whether there is a significant association between two variables. 

The chi square test for independence should be used when:

2. The variables under study are each categorical

2. The sampling  method is simple random sampling

1. Comment on Feb 25, 2015, 9:05 PM

Message collapsed. Message unread Re: Chi Square

posted by SAID SHEIK ABDI at Feb 25, 2015, 9:05 PM

Last updated Feb 25, 2015, 9:05 PM

3.

The chi-squared test of independence is one of the most basic and common hypothesis tests in the statistical analysis of categorical data.  Given 2 categorical random variables,  and , the chi-squared test of independence determines whether or not there exists a statistical dependence between them.  Formally, it is a hypothesis test with the following null and alternative hypotheses:

Chi-Square Goodness of Fit Test

When an analyst attempts to fit a statistical model to observed data, he or she may wonder how well the model actually reflects the data. How "close" are the observed values to those which would be expected under the fitted model? One statistical test that addresses this issue is the chi-square goodness of fit test. This test is commonly used to test association of variables in two-way tables (see "Two-Way Tables and the Chi-Square Test"), where the assumed model of independence is evaluated against the observed data. In general, the chi-square test statistic is of the form

http://www.ling.upenn.edu/~clight/chisquared.htm

·