The 95th percentile

The 95th percentile

Datadog Statistics Interview Question

Datadog reports the slow end of a response time distribution rather than the average, because an average hides the requests that make users leave.

Write p95_response_time(times) that returns the 95th percentile by nearest rank: sort the values, then return the one at position ceil(0.95 × n), counting from 1.

Asked of

  • Data Analyst
  • Analytics Engineer
  • Data Engineer
  • Data Scientist
  • ML Engineer
  • MLOps Engineer

Example 1

Input

times = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]

Output

19

Example 2

Input

times = [5, 1, 3]

Output

5

Example 3

Input

times = [42]

Output

42

Explanation

With 20 values, 0.95 × 20 is 19, so the answer is the 19th smallest. With 3 values, 0.95 × 3 is 2.85, which rounds up to 3, so the answer is the largest.

Submit also runs 2 hidden test cases that check edge cases.

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