DATA INSIGHTS · GMAT-DI-MSR-02 · DRAFT

Multi-Source Reasoning: Quantitative Synthesis

Combine independent sources while preserving definitions, denominators and time periods

Learn: Evidence and decisions

Build a source map before calculating

Note the time period, unit, population and definition in each tab. A figure can be numerically correct but irrelevant if it describes a different group or period.

Normalize before comparing

Use the stated denominator for a rate. When combining groups, add numerators and denominators first, then calculate the overall rate.

Separate observation from expectation

A target or forecast describes a threshold or expectation, not an observed result. Compare it with actual data only after identifying the matching measure.

Learning Objectives

Identify which source defines each measure and which provides its values.
Combine information across sources using consistent units and populations.
Distinguish actual results, targets and forecasts.
Select conclusions supported by all relevant evidence.

Prerequisite Knowledge

Fractions, percentages and ratios.
Reading tables and comparing rates.

Worked Examples

Compare conversion rates and evaluate a target

Region North receives 200 applications and approves 150. Region South receives 240 and approves 180. A policy requires at least a 72% approval rate in both regions. Which region has the higher rate, and does each satisfy the policy?

Use the definitions and denominators supplied for each region. $r_{N} = 150/200 = 75%, r_{S} = 180/240 = 75%$
Compare both observed rates with the 72% threshold. $75% \geq 72%$
Both rates are equal and both satisfy the policy.

Conclusion: Comparing approval counts alone would incorrectly favor South. The relevant comparison is each count divided by its own applications.

Compute a weighted combined rate

A service team resolves 72 of 90 requests in one district and 45 of 60 in another. Find the overall resolution rate.

Combine resolved requests and total requests before dividing. $r = \frac{72 + 45}{90 + 60} = \frac{117}{150} = 78%$
Check against the unweighted mean of the two district rates. $(80% + 75%) /2 = 77.5%$
The overall rate is weighted by request volume, not an equal average of districts.

Conclusion: The larger district contributes more requests, so its rate has greater weight in the combined result.

Compare an actual result with a forecast

A plan forecast 1,320 on-time deliveries from 1,500 shipments. The actual report shows 1,350 on-time deliveries from 1,500 shipments. Did the actual rate exceed the forecast rate, and by how many percentage points?

Calculate both rates using the same total shipments. $r_{f or ec a s t} = 1320/1500 = 88%, r_{a c t u a l} = 1350/1500 = 90%$
Subtract rates to obtain a percentage-point difference. $90% - 88% = 2 percentage points$

Conclusion: The actual result exceeded the forecast by 2 percentage points. A percentage-point difference is not a relative percent increase.

Think Like a GMAT Test-Taker

Read the question first and record the measure, period and population it asks about.

Open each source to locate its definitions and the matching values.

For a combined rate, aggregate the relevant counts before dividing.

Use only the evidence supplied; do not repair a source discrepancy with outside assumptions.

Common Traps

Comparing raw counts when sample sizes differ.

Averaging percentages without weighting by their denominators.

Treating a forecast or target as an actual result.

Combining data from different time periods or incompatible definitions.