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Estimate billboard reach and impressions

Last updated: Mar 29, 2026

Quick Overview

This question evaluates probabilistic modeling and statistical inference skills applied to audience measurement and attribution, covering Poisson-based frequency modeling, visibility-adjusted impressions, panel-based deduplication and expansion, uncertainty propagation (delta method/bootstrap), and Markov-chain attribution within the Statistics & Math / Data Science domain. It is commonly asked to test the ability to convert traffic and visibility inputs into quantitative reach and impressions with propagated confidence intervals, reason about attribution via a 3-state Markov chain, identify measurement biases, and demonstrates both conceptual understanding and practical application through numerical estimation and sensitivity analysis.

  • hard
  • Pinterest
  • Statistics & Math
  • Data Scientist

Estimate billboard reach and impressions

Company: Pinterest

Role: Data Scientist

Category: Statistics & Math

Difficulty: hard

Interview Round: Onsite

A single digital billboard sits beside a 6-lane urban expressway. You must estimate weekly unique reach (people who saw it at least once) and total impressions, and then extend to estimate conversion to store visits using a simple Markov chain model. Given data and assumptions: - Average weekday vehicles/day: 80,000; weekend: 50,000. Average occupants/vehicle: 1.4. - Visibility probability per pass depends on lane and time: p_vis = 0.75 (daytime), 0.55 (night), weighted by 70% daytime traffic. - Share of traffic by segment: locals living within 3 km (30%), commuters passing ≥4 weekdays (50%), occasional passers (20%). - For commuters, passes/week ~ Poisson(λ=5). For locals, passes/week ~ Poisson(λ=2). For occasional, passes/week ~ Poisson(λ=1). - Deduplicate unique people using mobile location panel of 120,000 devices/week within 500 m; device-to-person expansion factor: 2.2; panel capture rate uncertainty ±10% (1σ). Tasks: 1) Estimate weekly unique reach and total impressions with 95% CIs, clearly stating all formulas and independence assumptions. Show how you combine traffic counts, occupancy, visibility, and pass frequency to compute impressions, and how you deduplicate to people-level using the panel (include the capture-rate uncertainty via delta method or bootstrap). 2) Using a 3-state Markov chain (Unaware → Aware → Visit), propose reasonable transition probabilities by segment and compute expected visits/week attributable to the billboard. Discuss sensitivity of results to these probabilities and to p_vis. 3) Identify at least three major bias sources (e.g., panel selection, deduplication error, dwell-time bias) and propose corrections/validations.

Quick Answer: This question evaluates probabilistic modeling and statistical inference skills applied to audience measurement and attribution, covering Poisson-based frequency modeling, visibility-adjusted impressions, panel-based deduplication and expansion, uncertainty propagation (delta method/bootstrap), and Markov-chain attribution within the Statistics & Math / Data Science domain. It is commonly asked to test the ability to convert traffic and visibility inputs into quantitative reach and impressions with propagated confidence intervals, reason about attribution via a 3-state Markov chain, identify measurement biases, and demonstrates both conceptual understanding and practical application through numerical estimation and sensitivity analysis.

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Pinterest
Oct 13, 2025, 9:49 PM
Data Scientist
Onsite
Statistics & Math
3
0

Digital Billboard: Weekly Reach, Impressions, and Store-Visit Attribution

Context

You are estimating the performance of a single digital billboard beside a 6‑lane urban expressway over one week. You must report weekly unique reach (people who saw it at least once) and total impressions, then attribute store visits via a simple 3‑state Markov chain. Assume traffic counts refer to passes that could potentially see the billboard (directionality already accounted for), and average vehicle occupancy applies uniformly.

Given Data and Assumptions

  • Traffic counts
    • Weekday vehicles/day: 80,000 (Mon–Fri)
    • Weekend vehicles/day: 50,000 (Sat–Sun)
    • Average occupants per vehicle: 1.4
  • Visibility probability per pass
    • Daytime p_vis_day = 0.75; Night p_vis_night = 0.55
    • Daytime traffic share = 70% (thus weekly average p_vis = 0.7×0.75 + 0.3×0.55)
  • Audience segments (share of traffic by passes)
    • Commuters (≥4 weekdays): 50%
    • Locals (within 3 km): 30%
    • Occasional passers: 20%
  • Pass frequency per person by segment (weekly)
    • Commuters: Poisson(λ=5)
    • Locals: Poisson(λ=2)
    • Occasional: Poisson(λ=1)
  • Panel for deduplication
    • Weekly unique devices within 500 m: 120,000
    • Device-to-person expansion factor: 2.2
    • Panel capture-rate uncertainty: ±10% (1σ), to be propagated (delta method or bootstrap)

Tasks

  1. Estimate weekly unique reach and total impressions with 95% confidence intervals. Clearly state all formulas and independence assumptions. Show how to combine traffic counts, occupancy, visibility, and pass frequency to compute impressions, and how to deduplicate to people-level using the panel (including the capture-rate uncertainty via delta method or bootstrap).
  2. Using a 3-state Markov chain (Unaware → Aware → Visit), propose reasonable segment-specific transition probabilities and compute expected visits/week attributable to the billboard. Discuss sensitivity to these probabilities and to p_vis.
  3. Identify at least three major sources of bias (e.g., panel selection, deduplication error, dwell-time bias) and propose corrections/validations.

Solution

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