Question 3: Is there any evidence that induction of labour is related to the risk of a caesarean?
Induction of labour is a qualitative, dichotomous variable so we can do a chi-squared test or Fisher's exact test.
We get the following output:
Induction of labour * Caesarian section Crosstabulation | ||||
---|---|---|---|---|
Count | ||||
Caesarian section | Total | |||
No | Yes | |||
Induction of labour | No | 546 | 92 | 638 |
Yes | 155 | 46 | 201 | |
Total | 701 | 138 | 839 |
Chi-Square Tests | |||||
---|---|---|---|---|---|
Value | df | Asymp. Sig. (2-sided) | Exact Sig. (2-sided) | Exact Sig. (1-sided) | |
Pearson Chi-Square | 7.971 ^{a} | 1 | .005 | ||
Continuity Correction^{b} | 7.366 | 1 | .007 | ||
Likelihood Ratio | 7.509 | 1 | .006 | ||
Fisher's Exact Test | .006 | .004 | |||
Linear-by-Linear Association | 7.961 | 1 | .005 | ||
N of Valid Cases | 839 | ||||
a. 0 cells (.0%) have expected count less than 5. The minimum expected count is 33.06.. | |||||
b. Computed only for a 2x2 table |
The chi-squared test is valid, because the expected frequencies are all greater than five. The relationship is highly significant (chi-squared = 7.97, d.f. = 1, P = 0.005). Hence there is strong evidence that caesarean section is related to induction of labour.
We can also find the odds ratio by choosing Risk from Statistics in Crosstabs. We get:
Risk Estimate | |||
---|---|---|---|
Value | 95% Confidence Interval | ||
Lower | Upper | ||
Odds Ratio for Induction of labour (No / Yes) | 1.761 | 1.185 | 2.618 |
For cohort Caesarian section = No | 1.110 | 1.023 | 1.204 |
For cohort Caesarian section = Yes | .630 | .459 | .865 |
N of Valid Cases | 837 |
Hence the odds ratio is 1.76 with 95% confidence interval 1.19 to 2.62.
Back to Exercise: Caesarean section and obesity.
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This page maintained by Martin Bland.
Last updated: 21 February, 2012.