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This is a easy difficulty Analytics & Experimentation question, commonly asked during Take-home Project rounds at Roblox.

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This question is commonly asked for Data Scientist candidates at Roblox during technical interviews.

Compute diff-in-diff and pretrend flag | Roblox Interview Question

Q: Compute diff-in-diff and pretrend flag

This question evaluates understanding of difference-in-differences estimation, simple pretrend detection, and related data-processing competencies for experiment-like observational datasets.

You are given individual-level observational data for an experiment-like setting with:

period[i] ∈ {0,1}: 0 = pre period, 1 = post period
treatment[i] ∈ {0,1}: 1 = treated group, 0 = control group
outcome[i] ∈ ℝ: numeric outcome

All three arrays have the same length N, and row i corresponds to one observation.

Tasks

Compute the Difference-in-Differences (DiD) estimate of the treatment effect:

$\text{DiD} = (\bar{Y}_{T,post} - \bar{Y}_{T,pre}) - (\bar{Y}_{C,post} - \bar{Y}_{C,pre})$

where the bars denote sample means over the corresponding subsets.

Compute a pretrend flag using the following simplified rule:

Let $d_{pre} = |\bar{Y}_{T,pre} - \bar{Y}_{C,pre}|$ .
Given a real number threshold , return pretrend=True if $d_{pre} > \text{threshold}$ , else False .

Output

Return:

did_estimate (float)
pretrend (boolean)

Assumptions / edge cases

If any of the required cells (T/C × pre/post) has zero observations, specify and implement a reasonable behavior (e.g., raise an error or return NaN).

Tasks

Compute the Difference-in-Differences (DiD) estimate of the treatment effect:

\text{DiD} = (\bar{Y}_{T,post} - \bar{Y}_{T,pre}) - (\bar{Y}_{C,post} - \bar{Y}_{C,pre})

where the bars denote sample means over the corresponding subsets.

Compute a pretrend flag using the following simplified rule:

Let

d_{pre} = |\bar{Y}_{T,pre} - \bar{Y}_{C,pre}|

Given a real number threshold , return pretrend=True if

d_{pre} > \text{threshold}

, else False .

Compute diff-in-diff and pretrend flag

Quick Overview

Tasks

Output

Assumptions / edge cases

Solution

Comments (0)

Compute diff-in-diff and pretrend flag

Quick Overview

Tasks

Output

Assumptions / edge cases

Solution

Comments (0)