Calculate Conversion Lift CI
Company: Coinbase
Role: Data Scientist
Category: Statistics & Math
Difficulty: medium
Interview Round: Onsite
In an A/B test, the control group had 1,000 users and 120 conversions. The treatment group had 1,000 users and 150 conversions.
Using a normal approximation, calculate a 95% confidence interval for the **absolute lift in conversion rate** (`treatment - control`) by hand. Then state whether the result is statistically significant at the 5% level and explain the interpretation of the interval.
Quick Answer: This question evaluates statistical inference skills for proportions, specifically construction and interpretation of confidence intervals and hypothesis testing in A/B experiments using normal approximations.