observational studies

collect data in a way that does not directly interfere with hwo the data arise (\"observe\") only establish an association \"retrospective\":uses past data \"prospective\":data are collected througout the study

there may be a third variable that is responsible for both being slim and eating breakfast.

Relationship between two variables:breakfast cereal keeps girls slim

observational

experiment

studies

Observational Studies & Experiments

randomly assign subjects to treatments establish causal connections