Chi Test Flashcards
what does chi-square analysis consist of?
test how well the observed frequencies conform to the expected frequencies.
measures degree of fit between the observed and expected frequencies.
what is the symbol for chi square?
χ2
what does chi-square analyse?
in chi-square analysis, we analyse the frequencies that exist within categories
what does chi-square compare?
comparing observed (or obtained) frequencies with expected frequencies. The chi-square statistic expresses the discrepancy between the observed and expected frequencies.
how do we calculate expected frequencies?
Calculating the expected frequencies can be obtained by
–Goodness of fit
-Test of independence
describe chi test as a goodness of fit test
have a theory or hypothesis about how well the observed data should fit the expected data.
Describe Ho in goodness of fit test for chi square
Ho: The observed data does fit the expected data –Therefore, rejecting Ho is a statement that the data are at odds with the expected data.
i.e The obtained frequencies don’t differ from the expected frequencies
what is the df in goodness of fit test for chi-square analysis?
df for a goodness of fit test, is number of categories -1
formula for chi square analysis goodness of fit
what happens if we find a=0.045 df=1 thus critical chisquare value is 3.85 but obtained chi-value is 7.5?
reject Ho
There is a significant difference between the frequencies that we expect and the frequencies _we actually observed.
more than would be expected by chance._
This supports our research/alternative hypothesis that there is discrimination in this case based on gender.
what happens when X2obt > X2 critical value?
reject Ho
significant difference between the frequencies that we expect and the frequencies we actually observed. more than would be expected by chance.
when is chi-square analysis used?
chi-square statistic is used to evaluate the relative frequencies of events in a population that fall into well defined categories
for each category there is an expected frequency and observed frequency
describe chi-square as test of independence
test the independence of two variables on which frequency data are available.
what is the Ho for test of independence in chi-test?
two variables are independent
to reject the Ho in the test of independence is making a statement that
Rejecting the Ho is a statement that two factors are not independent, but related.
Give an example of retaining Ho and rejecting Ho
Retaining Ho is a statement that pet ownership and gender are independent in the population i.e., that knowing someone’s gender does not tell you anything about whether they might be likely to own a pet
Rejecting Ho: pet ownership is dependent upon gender
how to calculate df in test of independence?
df = (rows – 1)(columns – 1)
what happens when the X2obt is > X2critical value from the test of independence?
we reject the Ho
one can conclude that pet ownership is influenced by gender; they are not independent, but related.
