Suggested answers to exercise: Cough during the day or at night and history of bronchitis, 1

Question 1: Using SPSS, cross-tabulate cough by history of bronchitis. Carry out a chi-squared test of association.

Suggested answer

We choose Analyze, Descriptive Statistics, Crosstabs. Put the variable 'Bronchitis by age 5' into Row(s): and 'Day or night cough at age 12' into Column(s):. Click Statistics, Chisquare, Continue. Click OK.

You should get the case processing summary and then the following:

Bronchitis by age 5 * Day or night cough at age 12 Crosstabulation
Day or night cough at age 12 Total
Yes No
by age 5
Yes 26 247 273
No 44 1002 1046
Total 70 1249 1319

Chi-Square Tests
Value   df   Asymp. Sig.
Exact Sig.
Exact Sig.
Pearson Chi-Square 12.180a 1 .000
Continuity Correctionb 11.145   1 .001
Likelihood Ratio 10.609   1 .001
Fisher's Exact Test .001 .001
Linear-by-Linear Association 12.171   1 .000
N of Valid Cases 1319  
a 0 cells (.0%) have expected count less than 5. The minimum expected count is 14.49
b Computed only for a 2x2 table

We have chi-squared = 12.18, d.f. = 1, P < 0.001.

The test is highly significant and we have strong evidence that current cough at age 12 is associated with a history of bronchitis before age five.

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Last updated: 20 February, 2012.

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