Qualified respondents cannot exceed total screened.
Incidence Rate (IR)
0.00%
Total Participants Required to Screen
0
To achieve 0 completes at 0% IR, you need to invite enough people to get this many screener attempts.
function switchTab(tabName) {
// Update Tabs UI
var tabs = document.getElementsByClassName('mr-tab');
for(var i = 0; i < tabs.length; i++) {
tabs[i].classList.remove('active');
}
document.getElementById('tab-' + tabName).classList.add('active');
// Toggle Views
document.getElementById('view-calc-ir').style.display = 'none';
document.getElementById('view-calc-feasibility').style.display = 'none';
document.getElementById('view-' + tabName).style.display = 'block';
}
function calculateIncidenceRate() {
// 1. Get Elements
var screenedInput = document.getElementById('total-screened');
var qualifiedInput = document.getElementById('qualified-completes');
var resultBox = document.getElementById('result-ir');
var resultValue = document.getElementById('ir-output');
var explanation = document.getElementById('ir-explanation');
var errScreened = document.getElementById('err-screened');
var errQualified = document.getElementById('err-qualified');
// 2. Parse Values
var screened = parseFloat(screenedInput.value);
var qualified = parseFloat(qualifiedInput.value);
// 3. Reset Errors
errScreened.style.display = 'none';
errQualified.style.display = 'none';
resultBox.style.display = 'none';
// 4. Validation
if (isNaN(screened) || screened <= 0) {
errScreened.style.display = 'block';
return;
}
if (isNaN(qualified) || qualified screened) {
errQualified.style.display = 'block';
return;
}
// 5. Calculation Logic
var incidenceRate = (qualified / screened) * 100;
// 6. Formatting & Output
resultValue.innerHTML = incidenceRate.toFixed(2) + "%";
var difficultyText = "";
if(incidenceRate > 50) {
difficultyText = "High Incidence (General Population)";
} else if (incidenceRate > 20) {
difficultyText = "Moderate Incidence";
} else if (incidenceRate > 5) {
difficultyText = "Low Incidence (Niche Audience)";
} else {
difficultyText = "Very Low Incidence (Hard-to-Reach)";
}
explanation.innerHTML = "Category: " + difficultyText + ". For every 100 people screened, approximately " + Math.round(incidenceRate) + " qualify.";
resultBox.style.display = 'block';
}
function calculateFeasibility() {
// 1. Get Elements
var targetInput = document.getElementById('target-completes');
var irInput = document.getElementById('estimated-ir');
var resultBox = document.getElementById('result-feasibility');
var resultValue = document.getElementById('feasibility-output');
var targetText = document.getElementById('target-text');
var estIrText = document.getElementById('est-ir-text');
// 2. Parse Values
var target = parseFloat(targetInput.value);
var ir = parseFloat(irInput.value);
// 3. Validation
if (isNaN(target) || target <= 0 || isNaN(ir) || ir <= 0) {
alert("Please enter valid positive numbers for Target Completes and Estimated IR.");
return;
}
// 4. Calculation Logic: Screened = Target / (IR / 100)
var screenedNeeded = target / (ir / 100);
// 5. Formatting & Output
resultValue.innerHTML = Math.ceil(screenedNeeded).toLocaleString();
targetText.innerHTML = target;
estIrText.innerHTML = ir + "%";
resultBox.style.display = 'block';
}
How to Calculate Incidence Rate in Market Research
Incidence Rate (IR) is one of the most critical metrics in quantitative market research. It directly dictates the feasibility, cost, and duration of a study. Understanding how to calculate it accurately ensures that your project budget is realistic and your fieldwork timeline is achievable.
What is Incidence Rate?
In market research, Incidence Rate represents the percentage of people in a general pool of respondents who meet the specific criteria to participate in your survey. These criteria are usually determined by "screening questions" at the beginning of a survey (e.g., "Do you own a car?" or "Are you the primary grocery shopper?").
If you send a survey to a random group of people, the IR is the percentage that qualifies to complete the full questionnaire.
The Incidence Rate Formula
To calculate the actual incidence rate of a study currently in the field or recently completed, use the following formula:
IR (%) = (Qualified Respondents ÷ Total People Screened) × 100
Example Calculation
Imagine you launch a survey regarding electric vehicle ownership.
You send invitations and 2,000 people click the link and answer the screening questions (Total Screened).
Out of those, only 100 people actually own an electric vehicle and pass the screener (Qualified Respondents).
The calculation would be: (100 ÷ 2,000) × 100 = 5% Incidence Rate.
Why Does Incidence Rate Matter?
Incidence rate is the primary driver of Cost Per Interview (CPI).
High IR (e.g., >50%): Easy to find respondents. Costs are lower because fewer people need to be invited and screened to reach the target sample size.
Low IR (e.g., <5%): Difficult to find respondents. Costs are significantly higher because thousands of people must be screened out (and often compensated partially) just to find one qualified person.
Estimating Sample Needed (Feasibility)
Before launching a study, researchers often estimate the IR to determine how many people they need to reach. This is done using the reverse formula included in the "Estimate Sample Needed" tab of the calculator above:
Required Screeners = Target Completes ÷ (Estimated IR %)
If you need 400 completes and you expect a 10% incidence rate, you cannot simply invite 400 people. You must invite enough people to get 4,000 to click the link (400 ÷ 0.10).
Factors That Lower Incidence Rate
The more specific your screening criteria, the lower your IR will be. Common factors include:
Niche Demographics: High income, specific job titles, or narrow age bands.
Behavioral Traits: Frequent flyers, luxury car owners, or users of specific software.
Geographic Restrictions: Targeting a specific zip code vs. a whole country.
Use the calculator above to plan your next research project effectively by estimating the volume of traffic required to hit your survey goals.