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.