Question 1: Using SPSS, cross-tabulate cough by history of bronchitis. Carry out a chi-squared test of association.
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 | ||||
|---|---|---|---|---|
| Count | ||||
| Day or night cough at age 12 | Total | |||
| Yes | No | |||
| Bronchitis by age 5 | Yes | 26 | 247 | 273 |
| No | 44 | 1002 | 1046 | |
| Total | 70 | 1249 | 1319 | |
| Chi-Square Tests | |||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Value | df | Asymp. Sig. (2-sided) | Exact Sig. (2-sided) | Exact Sig. (1-sided) | |||||||||||||||||||||||||||
| 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.
Back to Exercise: Cough during the day or at night and history of bronchitis.
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Last updated: 20 February, 2012.