Is the free trial paying off?

HardSpotifycohortsconversionrevenueleft joinrank· 160 XP (40 per step)

Mock interview. You're interviewing for a senior analyst job on a subscriptions team. The interviewer explains: "New Premium subscribers get a 30-day free trial. Finance wants to know if it's worth it. You've got an hour, let's go step by step."

How the subscriptions table works:

A first-time subscriber's row has a trial_ends_on date. People coming back after cancelling get no trial, so their trial_ends_on is empty.
A trial converts if it wasn't cancelled on or before trial_ends_on (cancelled_on is empty, or later than trial_ends_on).
The data runs to 30 June 2026. Only judge trials that ended on or before 30 June 2026; later ones are still running.

Step 1: Conversion by start month

"Start with the basics: for each month in which trials started, how many trials were there, how many converted, and what's the conversion rate?"

Expected output

start_month as the first day of the month; conversion_rate as a percentage rounded to 1 decimal; sorted by start_month

Example of the shape (made-up values):

start_month	trials	converted	conversion_rate
2025-09-01	20	12	60.0

Hints, the later steps and the answer come with Pro.

Step 1 of 4

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