McNemar test (McNemar debate data) Four hundred registered voters are surveyed a
ID: 3178920 • Letter: M
Question
McNemar test (McNemar debate data)
Four hundred registered voters are surveyed about which of the two presidential candidates (Clinton and Trump) they prefer both before and after a televised debated between the two candidates. The debate SPSS data file contains 400 cases representing those voters who a) preferred Clinton before and after the debate; b) preferred Trump before and after the debate; c) preferred Clinton before the debate and Trump after the debate; and d) preferred Trump before the debate and Clinton after the debate.
1) What percentage of the 400 registered voters surveyed preferred Clinton before the debate? What percentage preferred Clinton after the debate?
2) How many total discordant pairs of before and after preferences are there?
3) Suppose that it was believed before the debate that Trump was not as good a debater as Clinton, so it was hypothesized that the proportion preferring Trump would decrease after the debate. Write the null and alternative hypotheses.
4) Write the results bases on the output
SPSS output of below.
Before & After
Before
After
Clinton
Trump
Clinton
190
26
Trump
14
170
Test Statisticsa
Before & After
N
400
Chi-Squareb
3.025
Asymp. Sig.
.082
a. McNemar Test
b. Continuity Corrected
Before & After
Before
After
Clinton
Trump
Clinton
190
26
Trump
14
170
Explanation / Answer
Result:
Before
After
Clinton
Trump
Total
Clinton
190
26
216
Trump
14
170
184
Total
204
196
400
Before: 216*100/400 = 54%
After: 204*100/400 = 51%
2) How many total discordant pairs of before and after preferences are there?
total discordant pairs =14+26 =40
3) Suppose that it was believed before the debate that Trump was not as good a debater as Clinton, so it was hypothesized that the proportion preferring Trump would decrease after the debate. Write the null and alternative hypotheses.
P1: proportion preferring Trump before debate:
P2: proportion preferring Trump after debate:
H0: P1=P2
H1: P1 > P2
This is one sided test
4) Write the results bases on the output
Calculated test value =3.025, P=0.082. This is two sided p value.
The one sided p value = 0.082/2 = 0.041 which is < 0.05 level of significance.
Ho is rejected.
We conclude that proportion preferring Trump would decrease after the debate.
Before
After
Clinton
Trump
Total
Clinton
190
26
216
Trump
14
170
184
Total
204
196
400