SQL and Stats Fundamentals | Dataford Interview Questions

Simple SQL and stats / probability

Write a PostgreSQL query that summarizes the observed outcome of each trial group. Calculate the number of non-missing trials, the number of successful trials, and the probability of success. Missing outcomes should not be included in the probability calculation.

Output

One row per trial_group
Columns: trial_group, observed_trials, successful_trials, and success_probability
Round success_probability to three decimal places
Order alphabetically by trial_group

Schema

experiment_trials

Column	Type	Description
trial_idPK	INT	Unique identifier for the trial
trial_group	VARCHAR(50)	Group assigned to the trial
outcome	BOOLEAN	Whether the trial was successful

Your question is SQL and Stats Fundamentals. Start with the requirements and the one table in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem

Simple SQL and stats / probability

Output

One row per trial_group
Columns: trial_group, observed_trials, successful_trials, and success_probability
Round success_probability to three decimal places
Order alphabetically by trial_group

Schema

experiment_trials

Column	Type	Description
trial_idPK	INT	Unique identifier for the trial
trial_group	VARCHAR(50)	Group assigned to the trial
outcome	BOOLEAN	Whether the trial was successful

Your question is SQL and Stats Fundamentals. Start with the requirements and the one table in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.