This interview question evaluates statistical assumptions, formulas, estimation strategy, uncertainty, edge cases, and interpretation in a realistic interview setting. A strong answer for Explain Central Limit Theorem and Its Limitations states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
##### Scenario
Assessing statistical knowledge for disease-testing model evaluation
##### Question
Explain the Central Limit Theorem, its prerequisites, and when it fails.
Describe Bayesian inference and why it is widely used.
A disease affects 1/1000 people. A test predicts positives with 95% accuracy and negatives with 98% accuracy. If the test flags someone positive, what’s the probability they are truly infected? Show your reasoning.
##### Hints
Discuss i.i.d. assumptions, sampling size, Bayes’ formula; build a confusion matrix and compute posterior probability.
Quick Answer: This interview question evaluates statistical assumptions, formulas, estimation strategy, uncertainty, edge cases, and interpretation in a realistic interview setting. A strong answer for Explain Central Limit Theorem and Its Limitations states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
You are assessing core statistical concepts used in evaluating diagnostic tests and in data science decision-making.
Assume:
"Predicts positives with 95% accuracy" refers to sensitivity: P(test+ | infected) = 0.95.
"Predicts negatives with 98% accuracy" refers to specificity: P(test− | not infected) = 0.98.
Questions
Central Limit Theorem (CLT)
Explain the CLT, its prerequisites/assumptions, and situations where it can fail or be unreliable.
Bayesian Inference
Describe Bayesian inference and why it is widely used in practice.
Disease Test Posterior Probability
A disease affects 1 in 1,000 people (prevalence = 0.001). A test has sensitivity 95% and specificity 98%.
If the test flags someone positive, what is the probability they are truly infected? Show your reasoning. You may use a confusion matrix and Bayes' rule.
Hints
Discuss i.i.d. assumptions and sample size for the CLT.
Use Bayes’ formula for the posterior probability.
Build a confusion matrix and compute the positive predictive value (PPV).
Clarifying Questions to Ask Guidance
Clarify the random variables, distributional assumptions, independence assumptions, and desired output.
Show enough derivation for the interviewer to follow the reasoning.
Explain how you would validate the result with simulation or sensitivity checks.
What a Strong Answer Covers Guidance
A correct setup with definitions, formulas, and boundary conditions.
A step-by-step derivation or estimation plan.
Interpretation of the result, including uncertainty and practical limitations.
Checks for assumptions, edge cases, and numerical stability.
Follow-up Questions Guidance
How would the result change if the assumptions were relaxed?
Can you verify the answer with a simulation?
What is the most likely source of estimation error?