Interview Q&A / Data Science
Data Science interview questions
Statistics, pandas, cleaning data and exploratory analysis for analyst and data science roles.
Prefer rapid revision? Practise Data Science short interview answers →
- What are variance and standard deviation, and why do we need them?
Variance is the average of the squared distances from the mean, and standard deviation is its square root. They measure how spread out the data is. Two datasets can have the same mean but very different spread, and standard deviation is easier to read because it is in the same units as the data.
BeginnerIn-depth3 min read - Why do we divide by n-1 when computing sample variance?
A sample sits closer to its own mean than to the true population mean, so dividing by n underestimates the population variance. Dividing by n-1 (Bessel correction) removes that bias on average.
IntermediateQuick answer1 min read