A few ways come to mind: Randomized double-blind studies peer reviewed question sets longitudinal cohorts The goal is to control for known biases. It’s hard

A few ways come to mind: Randomized double-blind studies peer reviewed question sets longitudinal cohorts The goal is to control for known biases. It’s hard, however, to discern conclusions from a dataset that is already biased. There’s very little in this to conclude effectively that “intellectual curiosity” was caused by birth order. They might be independent variables from each other on this survey born out by another variable. Or are completely spurious in nature.