>[!abstract] >The inspection paradox is a statistical illusion that arises whenever the probability of observing a quantity is related to the quantity being observed. >[!quote] >Suppose you ask college students how big their classes are and average the responses. The result might be 90. But if you ask the college for the average class size, they might say 35. It sounds like someone is lying, but they could both be right. When you survey students, you oversample large classes: If there are 10 students in a class, you have 10 chances to sample that class; if there are 100 students, you have 100 chances. In general, if the class size is x, it will be overrepresented in the sample by a factor of x ([[Downey, 2019]]). >[!related] >- **North** (upstream): — >- **West** (similar): [[Measurement problem]] >- **East** (different): — >- **South** (downstream): —