Question

quick self - quiz: association, causation, and confounding variables
an association is described. in each case, indicate
a) whether the statement implies causation or just association
b) a possible confounding variable

1. more ice cream sales tend to occur when more people drown.

(source: national weather service seasonal drowning statistics, 2018 - 2022)

1. “regular exercise reduces risk of depression” claims a headline reporting on a longitudinal study of adolescents.

(source: u.s. national institute of mental health, 2020)

1. taller students score higher on basketball tryouts.

(source: general trends reported by the national federation of state high school associations, 2019)
example 4: breakfast and concentration
in each case below, we describe a study to determine whether eating breakfast improves student concentration during morning classes. indicate whether each describes an experiment or an observational study.
(source: adolphus, k., et al. “the effect of breakfast on academic performance in children and adolescents.” frontiers in human neuroscience, 2013)
a) researchers survey a random sample of 150 students, recording whether they eat breakfast and comparing it with their first - period class performance.
b) in a different school, 150 students are randomly assigned: half eat a provided breakfast daily for two weeks, while the other half continue their usual routine. teachers then evaluate classroom focus.

Explanation:

1. a) Just association. Ice - cream sales and drowning are likely both affected by a third variable, not directly causally related. A possible confounding variable is temperature. Warmer weather leads to more ice - cream sales and more people swimming (and potentially drowning).
2. a) Implies causation. The headline suggests a cause - effect relationship where exercise causes a reduction in depression risk. A possible confounding variable could be overall lifestyle. People with a healthy lifestyle may be more likely to exercise and also less likely to be depressed.
3. a) Just association. Height may give an advantage in basketball tryouts, but it's not a strict cause - effect. A possible confounding variable is basketball experience. Taller students may be more likely to have played basketball before and thus perform better.
4. a) Observational study. The researchers are just observing and recording existing behaviors (eating breakfast or not) and performance, not manipulating any variables.

b) Experiment. The students are randomly assigned to different groups (eating breakfast or not), which is a key characteristic of an experiment.

Answer:

1. a) Just association

b) Temperature

1. a) Implies causation

b) Overall lifestyle

1. a) Just association

b) Basketball experience

1. a) Observational study

b) Experiment