Interview Q&A / Data Science
Data Science interview questions
Statistics, pandas, cleaning data and exploratory analysis for analyst and data science roles.
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- What are the main sampling methods: simple random, stratified, cluster and systematic?
Simple random gives everyone an equal chance; stratified splits the population into groups and samples each; cluster picks whole groups at random; systematic takes every kth item. Each trades cost against precision.
BeginnerQuick answer1 min read - What is sampling bias, and what are common types?
Sampling bias happens when the sample systematically differs from the population, so conclusions do not generalise. Common types are selection bias, survivorship bias, non-response bias and convenience sampling.
BeginnerQuick answer1 min read - How does sample size affect the margin of error in a survey?
For a proportion, margin of error is about 1.96 x sqrt(p(1-p)/n). It shrinks with the square root of n, so 1000 respondents give roughly +/- 3% and 400 give roughly +/- 5%, and reducing it further gets expensive quickly.
IntermediateQuick answer1 min read