14.5 Example: Skipping breakfast

The data in Table 14.6 come from a study of Iranian children aged 6–18 years old (Kelishadi et al. 2017). From this table:

The proportion of females who skipped breakfast is \(\hat{p}_F = 2\,383/6\,640 = 0.359\);
The proportion of males who skipped breakfast is \(\hat{p}_M = 1\,944/6\,846 = 0.284\).

Also,

\(\text{Odds}(\text{Skips breakfast, among F}) = 2\,383/4\,257 = 0.5598\);
\(\text{Odds}(\text{Skips breakfast, among M}) = 1\,944/4\,902 = 0.3966\).

For example, about 55.98 females skip breakfast for every 100 females who eat breakfast. The odds ratio (OR) comparing the odds of skipping breakfast, comparing females to males, is

\[\begin{align*} \text{OR} &= \frac{\text{Odds}(\text{Skipping breakfast, for females})}{\text{Odds}(\text{Skipping breakfast, for males})}\\ &= \frac{0.5598}{0.3966} = 1.41; \end{align*}\] the odds of females skipping breakfast are \(1.41\) times the odds of males skipping breakfast. The data can then be summarised numerically (Table 14.7).

TABLE 14.6: The number of Iranian children aged 6 to 18 who skip and do not skip breakfast
	Skips breakfast	Doesn’t skip breakfast	Total
Females	2383	4257	6640
Males	1944	4902	6846

TABLE 14.7: Numerical summary of the Iranian-breakfast data: Odds and percentage of those who skip breakfast
	Percentage	Odds	Sample size
Females	35.9	0.560	6640
Males	28.4	0.397	6846
Odds ratio		1.412

References

Kelishadi R, Mozafarian N, Qorbani M, Motlagh ME, Safiri S, Ardalan G, et al. Is snack consumption associated with meal skipping in children and adolescents? The CASPIAN-IV study. Eat Weight Disorders. 2017;22:321–8.