Make analysis reliable enough to support a decision
Technical skill in a consulting interview begins with dependable reasoning: choosing the right calculation, using consistent units, interpreting evidence and explaining what the result means. Depending on the role, it may also involve spreadsheets, programming or specialised analytical tools.
Quick Prep’s Technical Skills Enhancement focuses on the foundations that make those activities useful. It helps candidates who understand business concepts but lose accuracy under pressure, and those who can calculate quickly but struggle to connect the answer to a recommendation.
Role requirements should determine the depth. McKinsey describes expertise interviews and other assessments for some roles, while Bain also describes role-specific work and technical assessments. Use the instructions for your application to decide whether additional coding or specialist preparation is needed. McKinsey: Interviewing, Bain: Interviewing
Build quantitative fluency in a sensible order
Start with multiplication, division, fractions, ratios and percentage changes. Then practise weighted averages, contribution, break-even, growth rates and capacity. Add more complex concepts only when the basics remain reliable in unfamiliar examples.
Write the relationship before inserting numbers. If you are estimating annual revenue, identify customers, purchases per customer, price per purchase and the period. A short equation makes missing or duplicate assumptions easier to spot.
Use rounding deliberately. Estimate the order of magnitude first, then calculate to the precision the decision requires. State when the result is approximate. Rounding every intermediate step aggressively can create a material error even when each step looks reasonable.
Track units throughout. Thousands, millions, percentages, basis points, hours and days should remain visible. Many interview mistakes are unit errors disguised as arithmetic errors.
Worked drill: percentage change versus percentage points
Illustrative exercise.
A company’s operating margin rises from 10% to 12%. The increase is 2 percentage points and 20% relative to the original margin. Those describe the same change using different denominators.
If revenue falls from 10 million to 9 million, operating profit rises from 1 million to 1.08 million. Profit increases 8%, despite lower revenue.
The interpretation matters as much as the arithmetic. The company is earning more profit on a smaller revenue base. Next investigate whether the margin improvement reflects durable operating gains, a change in mix or a temporary cost reduction.
Practise explaining the distinction in one sentence. A number without its denominator is easy to misunderstand.
Read exhibits as evidence
Before calculating, inspect the title, axes, units, time period, sample and definitions. Ask whether the chart shows levels, changes, shares or an index. Check whether a truncated axis changes the visual impression.
Look for the pattern relevant to the objective. If the case concerns margin decline, a large segment with a small deterioration may matter more than a small segment with a dramatic percentage change.
Distinguish correlation from an explanation. If customer satisfaction and retention move together, that suggests a question; it does not by itself establish that a proposed satisfaction initiative will cause a specific retention improvement.
Worked drill: the weighted-average trap
Illustrative exercise with fictional figures.
A company has two products. Product A generates 80 million of revenue at a 10% margin. Product B generates 20 million at a 30% margin.
Operating profit is 8 million + 6 million = 14 million, so the total margin is 14%. Taking the simple average of 10% and 30% would incorrectly give 20%.
Now assume total revenue remains 100 million, but the mix changes to 60 million from A and 40 million from B. If the product margins stay unchanged, total profit becomes 6 million + 12 million = 18 million, giving an 18% margin.
The calculation suggests mix can improve profitability. A recommendation still needs to test demand, capacity and whether margins remain stable at the new volumes. It is not enough to say “sell more of B” without considering those conditions.
Develop disciplined data and spreadsheet habits
For a spreadsheet exercise, separate inputs, calculations and outputs. Use descriptive labels and consistent time periods. Reconcile subtotals, check signs and inspect extreme values. A model should be understandable by someone who did not build it.
For datasets, begin with the observation unit. Is each row a customer, transaction, account or event? Check missing values, duplicates, date ranges and filters before interpreting a result.
If a specialist role requires SQL or programming, practise the tasks named in the assessment guidance. Relevant examples may include joins, aggregation, data cleaning or communicating an analytical result. The tool is useful when it answers the business question accurately; knowing syntax alone is incomplete preparation.
Use a review loop that isolates the weakness
After a drill, classify the error. Did you misread the question, choose the wrong relationship, lose a unit, make an arithmetic slip or fail to explain the implication?
Repeat a different example targeting that specific step. For a denominator error, practise several weighted averages. For interpretation, write the business implication after every calculation. Then return to a full case to see whether the improvement holds under a broader task.
Keep accuracy and time records, but avoid treating speed as the only goal. A clear setup that prevents a major error can be more valuable than shaving seconds from multiplication.
Connect technical work with case performance
Use Finance Modeling when you need to build a complete economic model, and Case Interview Mastery to integrate calculations with structure and recommendations. The worked examples in the industry primers provide varied practice contexts.
Contact Quick Prep with the skills and assessment format you are preparing for so you can discuss relevant support. Drills and worked examples for every topic on this page sit alongside everything else organised by preparation stage.