Five Rings·Data Scientist·Technical Phone Screen
Jun 2026
Five Rings data scientist interview, all probability and statistics, coin problems back to back. Pretty brutal if your Bayesian intuition is rusty.
- You repeatedly toss a fair coin. What is the probability that the pattern HHH appears before the pattern THH?
- You toss a fair coin 15 times. What is the expected length of the longest consecutive run of heads?
- A coin has an unknown heads probability θ with prior density proportional to θ^3 on [0,1]. After observing 4 heads in 4 tosses, what is the posterior distribution of θ?
“This one tripped me up more than it should have.”