# The same app can have several valid rates

Companion to /learn/measurement/conversion-rate-definitions/

## Outcome
Calculate and compare rates without mixing events, populations or reporting periods.

Fictional example, not a client result.

## Scenario
Consider a fictional reporting sample with 10,000 impressions, 2,000 listing visitors, 400 install clicks and 300 completed installations. These are deliberately simplified counts, not a claim about a particular store’s report. Different ratios answer different questions, and none should be labelled merely “the conversion rate” without explanation.

## Reasoning
In this example, click-to-visitor rate is 400 divided by 2,000, or 20%. Completed-install-to-visitor rate is 300 divided by 2,000, or 15%. Completed-install-to-impression rate is 3%. The arithmetic is simple; the analytical risk is silently changing the event or denominator while retaining the same label.

## Action
Write the formula beside the chart and identify the reporting population. If a visitor-based rate moves from 15% to 18%, that is a three-percentage-point increase and a 20% relative increase. It is not proof that a creative change caused the movement. Check audience mix, dates and concurrent activity before moving from description to attribution.

## Trap to avoid
Do not compare rates across different stores, sources or time periods until the definitions are aligned. An attractive benchmark can be irrelevant if it counts a different action or excludes a different population.

## Advanced considerations
Inspect composition before interpreting an overall rate. If high-intent branded visitors become a smaller share of traffic, the combined rate can fall even when each segment behaves consistently. Compare meaningful segments using consistent definitions and avoid attributing a mix shift to a screenshot. When data is sparse, state that segmentation may be too noisy to support a firm decision.

## Exercise
A team reports a move from 10% to 12% as a “2% uplift.” Rewrite the statement so the arithmetic is unambiguous.

## Suggested answer
The rate increased by two percentage points, equivalent to a 20% relative increase. Add the event, denominator, audience and periods before presenting it as a real result. The statement still does not establish causation.

## Your worksheet

### Source report and exact metric name
Answer:
Evidence:
Uncertainty:
Owner:
Next action:

### Numerator event
Answer:
Evidence:
Uncertainty:
Owner:
Next action:

### Denominator and eligibility
Answer:
Evidence:
Uncertainty:
Owner:
Next action:

### Dates, audience and filters
Answer:
Evidence:
Uncertainty:
Owner:
Next action:

### Absolute percentage-point change
Answer:
Evidence:
Uncertainty:
Owner:
Next action:

### Relative change and attribution limits
Answer:
Evidence:
Uncertainty:
Owner:
Next action:

## Why the overall rate can fall without a segment getting worse
This constructed example keeps both segment rates constant while changing their shares of traffic. All actions and visitors use the same hypothetical definitions. It illustrates arithmetic, not an observed client result or a native store funnel.

Synthetic audience-mix example: each segment is unchanged, but the combined rate declines.
Segment | Period A: actions / visitors | Period B: actions / visitors
Higher-intent visitors | 160 / 400 = 40% | 80 / 200 = 40%
Other visitors | 60 / 600 = 10% | 80 / 800 = 10%
Combined population | 220 / 1,000 = 22% | 160 / 1,000 = 16%
Change in combined rate | Baseline: 22% | −6 percentage points; approximately −27.3% relative

### Calculate the combined rate from counts
Add the actions and eligible visitors, then divide. Do not take an unweighted average of segment percentages unless the denominators are equal. Period A has 220 actions among 1,000 visitors; Period B has 160 among 1,000. Both groups behave the same within the example, so changing the listing is not an explanation for the constructed decline.

### State the comparison precisely
The combined rate falls from 22% to 16%, a six-percentage-point decline. Relative change is (16 − 22) / 22, approximately −27.3%. Include the starting rate so a reader can reproduce the calculation. If the baseline is zero, relative change is undefined; if the eligible denominator is zero, the rate itself is undefined.

### Use segmentation without manufacturing certainty
In real data, inspect meaningful supported segments, their sizes and comparable definitions. Very small groups can produce unstable rates, and overlapping groups cannot simply be added. A mix explanation is a hypothesis until the underlying data supports it. Check that a reporting-definition change or duplicate events has not created the apparent composition shift.

## Continue reading
- /learn/measurement/aso-kpis/
- /learn/measurement/conversion-benchmarks/
- /learn/problems/low-product-page-conversion/