Probability Interview Formula Mistakes
Probability interview formula mistakes to avoid, including sample-space mismatch, independence assumptions, approximation misuse, and formula-first reasoning.
Candidates reviewing probability mistakes before interviews.
Formula-first reasoning
The biggest formula mistake is choosing a familiar expression before modeling the event. Setup decides the formula, not the other way around.
Sample-space mismatch
Counting ordered outcomes in one step and unordered outcomes in another step creates inconsistent denominators.
Independence assumptions
Multiplying probabilities usually needs independence or a conditional chain rule. If events affect each other, state the conditional probabilities instead.
Approximation misuse
Normal, Poisson, and independence approximations need conditions. Say when you are approximating and why the approximation is plausible.
Concrete check
For a dice-sum problem, ask whether the sums are equally likely. They are not; ordered pairs are equally likely.
Common mistakes
Candidates often memorize famous results without the assumptions. In interviews, explaining why a formula applies is part of the answer.
Practice the pattern
Use the LeetQuidity curriculum and calibration to turn this topic into a focused practice plan.