week 8

Question 1

which test assesses change over two time points on a single dichotomous variable

Answer 1

McNemar test - change between two time points ex. students thoughts on if a class should be required before and after taking the class

Question 2

cells B and C in a mcnemar test represent

Answer 2

change

Question 3

Mcnemar test only works for

Answer 3

dichotomous variables

Question 4

critical values of chi are always looked up with an

Answer 4

unsplit alpha

Question 5

chi square is an

Answer 5

omnibus test - shows that cells differ but not which ones

Question 6

how do you calculate DF for a mcnemar test

Answer 6

DF=1

Question 7

How are standardized residuals calculated in a bivariate chi-square analysis?

Answer 7

By dividing the difference between observed and expected frequencies by the square root of the expected frequency.

Question 8

When will the phi coefficient and Cramer’s v be identical?

Answer 8

When at least one of the variables has only two categories.

Question 9

When calculating Cramer’s v, what does k represent?

Answer 9

The number of rows or columns in the cross tabulation, whichever is less

Question 10

phi coefficient always ranges from

Answer 10

0-1

Question 11

t/f you can not have a negative phi coefficient

Answer 11

true because it is directly estimated from chi-square which is always positive

Question 12

as the size of cross-tabulation increases so does

Answer 12

value of chi-square

Question 13

how do you calculate the phi coefficient?

Answer 13

square root of obtained value of chi-square divided by overall N size

Question 14

how to calculate expected value

Answer 14

product of the marginal totals for the row and column in which the cell is located

Question 15

the simplest way to conceptualize a difference between two time points

Answer 15

mean difference

Question 16

what is the main difference between univariate and bivariate chi-square analysis

Answer 16

expected value calculations

Question 17

what is the bivariate chi-square

Answer 17

association between two categorical variables

Question 18

two bivariate applications of chi square

Answer 18

1. Change over time within a single variable
   - McNemar test
2. Association between categorical variables
   - phi coefficient, cramer’s v

Question 19

what kind of statistic is the mcnemar test

Answer 19

chi square statistic

Question 20

what kind of analysis is the mcnemar test

Answer 20

A repeated measures analysis
- must survey the same group of individuals twice
- intended to evaluate change over time

Question 21

what is null hypothesis for mcnemar test

Answer 21

no change

Question 22

in a 2x2 chi square analysis what will the DF be

Answer 22

always 1

Question 23

the mcnemar test only works for

Answer 23

dichotomous variables and designs with only two time periods

Question 24

cramers v and phi coefficient test what kind of data

Answer 24

nominal

Question 25

in a cross table what are we comparing

Answer 25

model fit for our observed data

Question 26

what can standardized residuals be treated as

Answer 26

may be treated like z-scores, with scores greater than +2 or less then -2 considered to be significant

Question 27

when can we consider a cell to be significantly different from our expectation

Answer 27

If the standardized residual is greater than +2 or less then -2

Question 28

t/f: chi square helps determine the magnitude of association

Answer 28

FALSE- it identifies if there is an association but not the magnitude

Question 29

phi coefficient ranges from

Answer 29

0-1, cant have negative phi coefficient bc it is a direct estimate from chi square and chi square cant be negative

Question 30

What can larger cross tabulation tables result in?

Answer 30

Phi coefficients > 1
- as the size of our cross tabulation (ie as the number of cells increases) the value of chi square tends to get larger. this is why the df for chi-square analysis is based on the number of rows and columns in our cross table
- this systematic increase in the size of the chi-square makes it increasingly likely that the chi coefficient will blow past our conceptual upper limit of 1 - thus we need to apply a correction factor to our phi coefficient so that the correlation still ranges from 0-1

Question 31

cross tables larger than 2x2 require a

Answer 31

correction

Question 32

what is the simplist corrected cross-tabular association

Answer 32

cramers v

Question 33

rule for chi square

Answer 33

80% of expected values have to be greater than 5, all expected values must be larger than one

Question 34

the magnitude of association is identified using

Answer 34

a phi coefficient or cramers v