Southern California Edison · Data Scientist
Updated · 2026-09-22

Southern California Edison Data Scientist
Interview Questions & Guide 2026

THE 60-SECOND BRIEF

As a Data Scientist at Southern California Edison (SCE), you are at the intersection of critical infrastructure and advanced analytics. Your work directly influences how one of the nation’s largest electric utilities plans its portfolio, manages renewable energy integration, and responds to the evolving power needs of millions of customers. You are not just building models; you are providing the data-driven insights necessary to maintain grid reliability and support the transition to a sustainable energy future.

Learn the economics of the product category before the loop. Marketplaces, subscription products and ad-supported products turn on different core quantities (match rate and liquidity, retention and churn, fill rate and yield) and fail in different characteristic ways.

PracHub has no confirmed round sequence for Southern California Edison. Treat the sections below as preparation areas and confirm the format with your recruiter.

Define numerator, denominator and window preciselyTurn a vague request into a measurable questionSize an experiment before anyone launches it

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See the practice prompts

12Practice promptsAcross five skill areas
3With worked solutionsIncluded in the practice prompts

As a Data Scientist at Southern California Edison (SCE), you are at the intersection of critical infrastructure and advanced analytics. Your work directly influences how one of the nation’s largest electric utilities plans its portfolio, manages renewable energy integration, and responds to the evolving power needs of millions of customers. You are not just building models; you are providing the data-driven insights necessary to maintain grid reliability and support the transition to a sustainable energy future.

The role involves high-stakes problem solving, often requiring you to translate complex technical concepts for stakeholders across various departments, including operations, meteorology, and finance. You will be expected to think "out-of-the-box," applying machine learning techniques to real-world utility challenges like short-term demand forecasting, renewable generation optimization, and demand response strategies. Success in this role requires a blend of rigorous statistical knowledge, a focus on productionalizing models, and the ability to thrive in a collaborative, cross-functional environment.

The role at SCE often requires a balance between pure data science and domain-specific forecasting. Be prepared to discuss how your models impact business decisions and operational efficiency.

01

Preparation focus

editorial

No round sequence has been reported for this company, so work the categories below and confirm the format with your recruiter.

What to demonstrate

  • Breadth across SQL, experimentation and product reasoning
  • Ability to state assumptions before choosing a method

How to prepare

  • Drill the practice exercises below and time yourself
  • Prepare three quantified stories about decisions you drove
PracHub interview preparation framework ↗

PracHub editorial advice for the preparation topics above.

01

Reading a pooled rate that moved because the mix moved, not because any behaviour changed

A pooled conversion rate is a weighted average, and a shift in the weights can move it in the opposite direction to every one of its parts. A paid campaign that brings low-converting traffic drops overall signup conversion even if desktop, mobile web and app conversion each rose that week, which is Simpson's paradox and it is the single most common cause of an inexplicable dashboard move. The discipline is to decompose before explaining: recompute the rate holding last period's segment weights fixed, and compare that counterfactual to the actual, so the mix effect and the rate effect are separated numerically rather than argued about. Segment on the dimensions that actually reweight, which in this domain are almost always device_type, referrer_channel, country and new versus returning.

02

Treating last-touch attribution as the causal value of a channel

The attribution label on dim_user is the output of a rule that assigns full credit to whichever touch happened to be recorded last inside a lookback window, and that rule systematically rewards channels that sit close to the conversion, especially branded search and retargeting, which largely intercept demand that already existed. Reallocating spend on those labels moves budget toward the channels that are best at being last, which is why attributed return on ad spend often improves while total signups do not. Nothing in the touchpoint data can settle this, because the counterfactual of not running the channel was never observed. The credible reads are a geo holdout or a scheduled pause, sized in advance on the total-signups metric rather than on the attributed one, and the honest framing in the meantime is that the label describes correlation with conversion and not incremental contribution.

03

Answering a product-sense question with a list of features

Answer with a decision and the measurement that would settle it: the hypothesis, the primary metric, the guardrails, and the result that would make you not ship. A feature brainstorm cannot be wrong, which is exactly why it earns no points.

04

Explaining an aggregate move without decomposing the mix shift

Split the change in the aggregate into within-segment movement and movement in segment weights before you explain it. Every segment's rate can fall while the overall rate rises, purely because volume shifted toward segments that already had higher rates.

Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.

8 technical prompts3 include a worked solution

Simulate the false positive cost of repeated peeking

mediumWorked solution
simulationpeekingtype i error

Quantify the cost of peeking. Simulate a two-arm experiment with no true effect: each arm accumulates Bernoulli conversions at a base rate of 0.10 up to 40,000 units per arm. Run a two-sided two-proportion z-test at alpha 0.05 at ten equally spaced interim points, and record whether the test ever crossed. Report the false positive rate over at least 10,000 replications, alongside the rate for a single look at the final sample only. Use a fixed seed and report a Monte Carlo standard error on both figures.

Approach
  1. Generate each replication as two cumulative sums of Bernoulli draws, then read the interim points off the cumulative arrays. Regenerating data at each look would make the looks independent, which destroys exactly the dependence the exercise is about: later looks share data with earlier ones.
  2. Use the pooled-variance two-proportion z: p_pool = (x1+x2)/(n1+n2), z = (p1-p2) / sqrt(p_pool*(1-p_pool)*(1/n1 + 1/n2)), reject when |z| > 1.96. State that the normal approximation is fine here because the smallest look has roughly 400 expected conversions per arm.
  3. Vectorise across replications rather than looping: draw a (reps, n) array of uniforms, threshold at 0.10, cumsum along axis 1 and slice the ten look indices. A per-replication loop at 10,000 by 40,000 is unnecessarily slow.
  4. Record the any-cross indicator per replication, take the mean, and compute the Monte Carlo standard error as sqrt(p*(1-p)/reps) so the reported figure comes with its own precision.
  5. Report the single-look rate in the same run as a control. If it does not land near 0.05, the bug is in the test statistic and not in the peeking argument.
Worked solution 30 min
  1. rng = np.random.default_rng(seed); for memory, batch the replications in chunks and accumulate the any-cross count across chunks.
  2. Per chunk: draw (chunk, 40000) uniforms per arm, x = (u < 0.10).cumsum(axis=1), slice columns at indices 3999, 7999, ..., 39999.
  3. Compute the ten z statistics vectorised over the chunk, take crossed = (np.abs(z) > 1.96).any(axis=1).
  4. Aggregate: peek_rate = total_crossed / reps; single_rate = mean of |z_final| > 1.96; mc_se = sqrt(p*(1-p)/reps) for each.
EXPECTED RESULTThe single-look rate lands at 0.05 within about 0.005 at 10,000 replications. The ten-look rate lands near 0.19, which with 10,000 replications has a Monte Carlo standard error of about 0.004, so anything in roughly 0.18 to 0.20 is consistent and anything near 0.40 indicates independent redraws.
Follow-up
  • Re-run with 40 looks instead of 10. Why does the curve flatten rather than continue rising linearly?
  • Among the replications that crossed, what is the mean observed lift, and why is it not zero?
  • What does an O'Brien-Fleming boundary or an always-valid confidence sequence change about this simulation, and what does each cost in power?

Cluster bootstrap for a per-session rate randomised on users

hard
cluster bootstraprandomisation unitvariance

An experiment randomised on user_id reports a per-session conversion rate, so sessions inside a user are correlated. Input: one row per session with user_id, variant in {control, treatment} and converted in {0,1}. Write a cluster bootstrap from scratch: resample users with replacement within each arm, keep every session of a drawn user, recompute each arm's ratio of converted sessions to sessions, and take the difference. Return the point estimate, a 95 percent percentile interval from at least 2,000 resamples, the naive session-level interval that ignores clustering, and the ratio of their widths.

Approach
  1. Name the estimand precisely: it is a ratio of sums, sum(converted) over sum(sessions) within an arm, not the mean of per-user rates. Those differ whenever session counts vary across users, and the ratio is what the reported metric is.
  2. Resample the cluster, not the row. Draw n_users user ids with replacement inside each arm and take every session belonging to each draw, including duplicate draws of the same user. Keeping the user count fixed per arm rather than the session count is what preserves the sampling design.
  3. Precompute per-user (converted_sum, session_count) once, so each resample is two vector lookups and a division rather than a repeated filter over the session frame. That turns 2,000 resamples from minutes into under a second.
  4. Take the 2.5th and 97.5th percentiles of the 2,000 differences for the interval, and report the point estimate from the full data rather than from the bootstrap mean, since the bootstrap mean carries the resampling bias.
  5. Compute the naive interval from the session-level binomial standard error and compare widths. The expected inflation is roughly sqrt(1 + (m-1)*rho), with m the mean sessions per user and rho the intraclass correlation of converted within users, so a computed ratio far from that value points at a bug in one of the two intervals.
Follow-up
  • Users average 3.4 sessions and the intraclass correlation is 0.12. What width ratio do you predict before running it, and does your bootstrap land there?
  • Give the delta-method standard error for this ratio and say when you would prefer it to the bootstrap.
  • Half the users in the treatment arm have exactly one session. What does that do to the cluster bootstrap's coverage, and how would you check it?

Rebuild per-visitor ordering without groupby convenience methods

easy
pandasvectorisationwindow logic

You have a DataFrame of 2 million fct_event rows with visitor_id, occurred_at_utc and event_id, unsorted and containing duplicate timestamps within a visitor. Produce three new columns: event_rank, the 1-based position of the event within its visitor ordered by occurred_at_utc; seconds_since_prev, the gap to that visitor's previous event, NULL for the first; and is_first_for_visitor. You may use sort_values, shift, cumsum, numpy and boolean masking. You may not use groupby.transform, groupby.apply, groupby.cumcount, groupby.rank or merge_asof. Break timestamp ties on event_id.

Approach
  1. Sort once by ['visitor_id', 'occurred_at_utc', 'event_id'] and reset the index. The whole exercise reduces to row arithmetic on a sorted frame, and the tiebreak on event_id is what makes the result reproducible across runs.
  2. Mark visitor boundaries with is_first = df['visitor_id'].ne(df['visitor_id'].shift()). This is the single fact every other column derives from.
  3. Compute seconds_since_prev as the diff of the timestamp column, then overwrite it with NaT/NaN wherever is_first is True. The shift crosses the boundary between visitors and will otherwise hand the first row of each visitor the last event of the previous one.
  4. Build event_rank from a running counter that resets at boundaries: take a global cumulative position (np.arange(len(df))) and subtract, per row, the global position at which that visitor started. Get the start position by forward-filling the positions where is_first is True, which is a cumsum-free reset and is O(n).
  5. Verify against the forbidden method once, as a test rather than as the implementation, and confirm the two agree on every row.
Follow-up
  • The frame does not fit in memory. How does your approach change if you can only process one visitor-partitioned chunk at a time?
  • occurred_at_utc is client-supplied and sometimes runs backwards within a visitor. Does your seconds_since_prev go negative, and should it?
  • How would you extend this to reset the counter at every change of surface as well as visitor?

Four days spend equal time on query work, statistics, modelling and product judgement at deliberately shallow depth, which produces a scored map of where you actually stand. The last three days spend everything on the two areas the role weights most, and close by re-running day one to measure movement.

Small steps. Visible outcomes.0 / 7 completed
ONE WEEK · YOUR PACE

Prepare, practise & reflect

One practical outcome each day. Spend longer where you need it.

0 / 7 done
01Breadth pass: query fluency
  • Solve six prompts spanning aggregation, joins, window functions and date arithmetic in 60 minutes total, stopping at 10 minutes each whether or not it works, and mark every prompt as solved, solved slowly, or stuck.
  • For each unsolved prompt write the single blocking sentence (I lost the grain, I did not know the frame clause, I could not express the date boundary) instead of reading the solution.
  • Translate one pandas transformation you know well into SQL and one SQL query into pandas, checking that both return the same row count and the same totals.

Deliverable: A scored six-row table, one line per prompt, saved for the day-seven re-run.

Practice prompt ↗Practice prompt ↗Worked solution ↗
02Breadth pass: statistics and inference
  • Answer ten short questions in writing with nothing open: what a p-value is conditional on, what a 95 percent interval covers across repeated samples, when a paired test is the right one, what the bootstrap estimates, why multiple comparisons inflate false positives, how controlling the family-wise error rate differs from controlling the false discovery rate, what power depends on, what a missed real effect costs a product, the three situations where the central limit theorem does not rescue you (small n, very heavy tails, dependent observations), and what a standard error is the standard deviation of.
  • Grade yourself against a reference and count only the answers that were exactly right, not the ones that were nearly right.
  • Rewrite the two weakest answers the following morning from memory in full sentences.

Deliverable: Ten graded answers with an honest count of exact hits.

Practice prompt ↗Practice prompt ↗
03Breadth pass: modelling
  • Take one tabular dataset end to end in 90 minutes: a leakage-safe split, a baseline that is not a model (majority class or historical mean), one regularized linear model, one gradient-boosted tree, and a single evaluation metric chosen before you look at any result.
  • Write why that metric fits the cost structure: precision at a fixed recall for alerting, calibration for anything feeding a price or a threshold, ranking metrics for retrieval, and note that area under the ROC curve is insensitive to class balance in a way that can flatter a rare-positive problem.
  • Name the leak you were most likely to introduce (an encoding fit on all rows before splitting, or a feature computed after the label's timestamp) and write the check that would have caught it.

Deliverable: A notebook whose first cell states the metric and the baseline, plus two lines on what beat what and by how much.

Practice prompt ↗Practice prompt ↗
04Breadth pass: product judgement
  • Answer three case prompts aloud at 15 minutes each, timing how long passes before you state a success metric.
  • For one case write the first segmentation you would run and the row counts you expect per segment, so that a tiny segment cannot quietly drive the conclusion.
  • Take a metric definition you did not write, from a public dashboard, a textbook, or documentation you already have open, and list every place two analysts implementing it would diverge: which rows the denominator admits, whether the unit is an account or a person, what the time window is anchored to, and what happens to data that arrives late. Then write the one question that would close the largest of those gaps.

Deliverable: Three recorded case answers plus an ambiguity list for a metric someone else defined, ending in the single question you would ask about it.

Practice prompt ↗Practice prompt ↗Worked solution ↗
05Depth, first area
  • Rank the four areas by how many bullet points in the role description each one covers, pick the top one, and spend the entire day inside it.
  • Work the six hardest problems you can find in that area and for each write the generalizable move you should have reached for first, rather than the answer.
  • Re-solve the two you failed the same evening with notes closed.

Deliverable: Six generalizable moves written as instructions to yourself, not as solutions.

Practice prompt ↗Practice prompt ↗
06Depth, second area, and the seam between them
  • Repeat the depth protocol on the second-ranked area with the same six-problem structure.
  • Construct one problem that requires both areas at once, for example a metric redefinition whose effect you must validate with a test whose readout you then have to query.
  • Solve your own combined problem end to end and note where the handoff between the two areas cost you time.

Deliverable: One combined problem, solved end to end, with the handoff failure written down.

Practice prompt ↗
07Integration and re-measurement
  • Re-run the six prompts from day one under the same clock and compare both correctness and time.
  • Run a 60-minute mixed mock that moves between areas without warning, since switching cost is what breadth passes do not train.
  • Write the two areas you would still fail on, and the sentence you will use in the interview when you hit one of them.

Deliverable: A before-and-after score table plus a written plan for the two remaining gaps.

Practice prompt ↗Worked solution ↗

Expand any day for tasks and deliverables. Your progress is saved on this device.

Saying no well is a senior skill and it is rarely rehearsed. Think of a time you told someone their analysis was not worth doing, or that the experiment could not answer their question at the sample size available. Explain what you offered instead. Refusal without an alternative reads as obstruction rather than judgement.

Can you describe a project where you collaborated across multiple depa…

medium
behavioural and stakeholder questions

Can you describe a project where you collaborated across multiple departments?

Approach
  1. Name the disagreement or constraint, and how you resolved it with evidence.
  2. Close with what you would do differently, concretely.
  3. Quantify the outcome, including what you would not claim credit for.
Follow-up
  • What did you decide not to do, and why?
  • How did you know the outcome was caused by your change?

Tell me about a situation where you had to adapt your communication st…

medium
behavioural and stakeholder questions

Tell me about a situation where you had to adapt your communication style to work effectively with different roles.

Approach
  1. Pick a story where you drove the decision, not one where you observed it.
  2. Name the disagreement or constraint, and how you resolved it with evidence.
  3. State the situation in two sentences and spend the rest on your reasoning.
Follow-up
  • How did you know the outcome was caused by your change?
  • What did you decide not to do, and why?

Describe a time you had to explain a complex technical model to a non-…

medium
behavioural and stakeholder questions

Describe a time you had to explain a complex technical model to a non-technical stakeholder.

Approach
  1. Name the disagreement or constraint, and how you resolved it with evidence.
  2. Pick a story where you drove the decision, not one where you observed it.
  3. State the situation in two sentences and spend the rest on your reasoning.
Follow-up
  • How did you know the outcome was caused by your change?
  • What did you decide not to do, and why?

How do you handle disagreements within a project team?

medium
behavioural and stakeholder questions

How do you handle disagreements within a project team?

Approach
  1. Pick a story where you drove the decision, not one where you observed it.
  2. State the situation in two sentences and spend the rest on your reasoning.
  3. Quantify the outcome, including what you would not claim credit for.
Follow-up
  • How did you know the outcome was caused by your change?
  • What would you do differently if you ran that project again?
  • 01

    Can you describe a project where you collaborated across multiple departments?

  • 02

    Tell me about a situation where you had to adapt your communication style to work effectively with different roles.

  • 03

    Describe a time you had to explain a complex technical model to a non-technical stakeholder.

  • 04

    How do you handle disagreements within a project team?

PracHub interview preparation framework ↗
Is this an official Southern California Edison interview guide?

No. It is PracHub's own research and practice material for the Data Scientist role at Southern California Edison. Rounds and questions reflect what candidates have reported, not a process Southern California Edison has published, and they change over time. Confirm the current format and scope with your recruiter.

PracHub interview research ↗
How difficult are the technical portions of the interview?

The technical portions are generally conceptual and focused on your methodology rather than live coding. You should be prepared to discuss the "how" and "why" of your past technical work.

PracHub interview research ↗
What is the most important factor for success?

Successful candidates are those who can clearly articulate how their technical skills solve real business problems. Being able to explain your work to non-technical stakeholders is a significant differentiator.

PracHub interview research ↗
How long is the interview process?

The process is typically efficient, often moving from a screen to a panel interview within a few weeks. However, final decisions may take time as they align with internal team needs.

PracHub interview research ↗
Is there a coding test?

Most reports indicate that the interview process is primarily focused on behavioral questions and conceptual technical discussions rather than live coding challenges.

PracHub interview research ↗
Sources & methodology 3 sources ↗

No official company page is cited. Rounds and questions come from candidate reports and PracHub editorial material; each source shows the date it was read.