BCG Gamma DS Interview

EY
shaqbird

Go to company page EY

shaqbird
Mar 16, 2019 25 Comments

Hi, got contacted for a DS interview by BCG Gamma. How much of the interview process revolves around machine learning/advanced modeling vs traditional cases? Best ways to prepare? Thanks!

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  • GrubHub / Eng
    lumpydog

    Go to company page GrubHub Eng

    PRE
    Qualcomm
     lumpydog
    I did this interview very recently. It was case-based and he asked very interesting questions, here are my notes:

    Case Interview : client is facing a problem and we want to fix it w/ my experience, Design experiment .

    Context: fast moving consumer retailer: eg 7/11 or target.
    Local promotions for items on sale w/ discount
    Client is trying to evaluate the benefits of coordinated national marketing
    What is the optimal discount that should pursue

    All promotions at the client run weekly, meaning they start Monday and end on Sunday
    No canablization across products, all product sales are independent
    Price elasticity is linear. If you raise the price, demand doesn’t really drop.

    Question: Exploratory w/ Linear Regression to show price elasticity for each different product. Predict price elasticity.

    The first one was to formulate a linear regression model to predict units sold given price. Then you can use coefficient on the predictor price as an indicator of price elasticity. Meaning for a unit increase of price you’ll see w increase in Sales. Where w will probably be negative or very small positive. It would be small positive if the item is inelastic to price, for example, gas. For example, if gas price increases, volume will not decease as much as luxury products for example.

    He then posed a harder problem which I wasn’t able to solve, but given that we have a model for each product to predict units sold, and a budget for a whole store, how much should be price each item?

    I formulated it as a linear combination of prices and elasticity: $Product1 * w1 + $product2 * w2 + … + $product_i * wi <= BUDGET. How do you choose the prices now? This is a constrained optimization problem.

    THEN, he posed a very interesting question, albeit a bit flawed for the interview context, about RF regression. We take that same data for the linear model and fit it using a RF regression. He then said the client complained that the fit isn’t monotonic, or in other words, it has a flat spots and this is wrong. WHY?

    This is b/c the DT fitting routine recursively splits the decision space. In this case, ti just finds the median/mean of the points at the split and draws a straight line. regtree2.png . Therefore if you don’t have enough estimators in your RF, you will see the flat spots!
    Mar 16, 2019 8
    • BCG
      kashur

      Go to company page BCG

      kashur
      A few comments here are misleading. A core part of a BCG Gamma DS' role is coding and hardcore ML. This particular interview question set is focused on testing the critical thinking and strategic application of a potential data scientist, rather than testing the knowledge of intricacies within deep learning algorithms.

      In general, a Gamma data scientist spends ~70% of their time coding large-scale ML pipelines and algorithms, and the rest on the strategic and business aspects.
      Apr 14, 2021
    • PwC
      billsh

      Go to company page PwC

      billsh
      @bcg, what would be the other things to check (in f2f setting) ?

      Or are all interviews case interviews with focus on conceptual understanding?
      Apr 20, 2021
  • I interviewed and failed. All interviews were pretty much cases but data intensive. Sample cases - you are working with a oil company. (1) you are helping them price oil (in real-time ) for all their gas stations in Texas . How will you approach it. What data you want to see. (2) citi bike in new york city. How you define the strategy to rearrange bikes between locations. (3) working with a grocery chain, how you will define their loyality program. What data you want to capture. How do you define a model to issue coupons to increase sales. Hope this helps.
    Mar 16, 2019 8
  • Careem
    oNlO06

    Go to company page Careem

    oNlO06
    How do you do the hackerrank test? I solved it and passed all test cases still got a reject
    Apr 29, 2020 1
  • Curious too. Tried to break into MBB a while back
    Mar 16, 2019 1
  • ShareThis
    mLgV45

    ShareThis

    mLgV45
    Has anybody had the business case for bcg gamma? I have one in a few days and would like do get a sense of what it is about
    Apr 25, 2021 0