## 2.4 Exercises

- What is a general term used for methods that assess the association between an outcome and one or more predictors?

- Correlation
- T-test
- Regression
- Analysis of variance

True or false? A simple linear regression model has only one predictor.

True or false? The outcome in a binary logistic regression model can take on only two possible values (e.g., presence or absence of a disease).

True or false? Regression methods can estimate the extent of effect modification by controlling for confounding.

Which of the following are valid purposes for regression?

- Controlling for confounding
- Estimating the magnitude of effect modification
- Testing an association
- All of the above

- Match the outcome type with the appropriate definition.

Outcome Type | Definition |
---|---|

Nominal | Has a small number of possible values. |

Binary | A categorical variable in which the levels have a natural ordering. |

Continuous | A categorical variable in which the levels do not have a natural ordering. |

Event time | Takes on non-negative integer values (0, 1, 2, …) and describes a number of items or events. |

Ordinal | Has a range of possible values and can take on any value in an interval. |

Count | Describes the time from a time origin to an event. |

Categorical | A categorical variable with exactly two levels. |

- Match the outcome type with the appropriate regression method.

Outcome Type | Regression Method |
---|---|

Nominal | Linear |

Binary | Cox |

Continuous | Poisson |

Event time | Multinomial logistic |

Ordinal | Binary logistic |

Count | Ordinal logistic |

For the following research questions, the wording assumes the outcome is mentioned first. For example, “Is (outcome) associated with (predictor)”? For example, for the research question “Is the prevalence of Type 2 diabetes mellitus (T2DM) associated with median household income?” the outcome is prevalence of T2DM and the predictor is median income.

For each of the following research questions:

- What is the outcome type (continuous, binary, ordinal, nominal, count, or event time)?
- What is the appropriate regression method?

Is total cholesterol associated with weight?

Is time to ischemic heart disease associated with binge drinking? (Degerud et al. 2021)

Is seropositivity for COVID-19 (positive/negative) associated with occupation? (Alsuwaidi et al. 2021)

Is hospital length of stay in days following surgery associated with age?

Is body mass index category (underweight, normal, overweight, obese) associated with hours of vigorous activity per week?

### References

*International Journal of Epidemiology*50 (4): 1077–90. https://doi.org/10.1093/ije/dyab077.

*American Journal of Epidemiology*190 (8): 1592–1603. https://doi.org/10.1093/aje/kwab063.