Suggested answers to exercise: Outcome of the MRC streptomycin trial, 1

Question 1: Using SPSS, cross-tabulate outcome by treatment group and carry out a chi-squared test of linear association.

Suggested answer

We choose Analyze, Descriptive Statistics, Crosstabs. Put the variable 'Radiological assessment' into Row(s): and 'Treatment' into Column(s):. Click Statistics, Chisquare, Continue. Click OK.

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

Radiological assessment * Treatment Crosstabulation
Count
Treatment Total
Streptomycin Control
Radiological
assessment Considerable improvement 28 4 32
Moderate/slight improvement 10 13 23
No material change 2 3 5
Moderate/slight deterioration 5 12 17
Considerable deterioration 6 6 12
Death 4 14 18
Total 55 52 107

Radiological assessment * Treatment Crosstabulation
Count
	Treatment	Total
Streptomycin	Control
Radiological assessment	Considerable improvement	28	4	32
Moderate/slight improvement	10	13	23
No material change	2	3	5
Moderate/slight deterioration	5	12	17
Considerable deterioration	6	6	12
Death	4	14	18
Total	55	52	107

Chi-Square Tests
Value df Asymp. Sig.
(2-sided)
Pearson Chi-Square 26.966^a 5 .000
Likelihood Ratio 29.612 5 .000
Linear-by-Linear Association 17.761 1 .000
N of Valid Cases 107
^a 2 cells (16.7%) have expected count less than 5.
The minimum expected count is 2.43.

Chi-Square Tests
	Value	df	Asymp. Sig. (2-sided)
Pearson Chi-Square	26.966^a	5	.000
Likelihood Ratio	29.612	5	.000
Linear-by-Linear Association	17.761	1	.000
N of Valid Cases	107
^a 2 cells (16.7%) have expected count less than 5. The minimum expected count is 2.43.

The linear association test gives chi-squared = 17.761 with P = .000, which we should write as P < 0.001.

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Last updated: 15 November, 2006.