Google Data Scientist I interview questions

General Statistics In what situation would you consider mean over median? For sample size n, the margin of error is 3. How many more samples do we need to make the margin of error 0.3? What is the assumption of error in linear regression? (Solution) Given data from two product campaigns, how could you do an A/B test if we see a 3% increase for one product? Statistical Probability I have a deck and take one card at random. What is the probability you guess it right? Explain a probability distribution that is not normal and how to apply that. Given uniform distributions X and Y and the mean 0 and standard deviation 1 for both, what’s the probability of 2X > Y? (Solution) There are four people in an elevator and four floors in a building. What’s the probability that each person gets off on a different floor? Make an unfair coin fair. (Solution) Machine Learning If the labels are known in a clustering project, how would you evaluate the performance of the model? Why use feature selection? (Solution) If two predictors are highly correlated, what is the effect on the coefficients in the logistic regression? What are the confidence intervals of the coefficients? What is the difference between K-mean and EM? When using a Gaussian mixture model, how do you know it is applicable?