Definition of the incidence rate
The incidence rate is defined as a frequency evaluator that helps to measure an incident or a disease etc. that occurs over a specific period. It is also referred to as IR. The incidence rate or IR is articulated as a fraction and can also be expressed as a percentage.
Understanding of the incidence rate
In medical science, the incidence rate is described as the number of new cases within a period as a proportion of the number of people who are considered a risk for the disease. Its formula is
Incidence = new cases / total population
For example, in a town, there are one thousand people and out of these two hundred are infected with a major disease over two years of observation. The incidence proportion is then 200 cases per 1,000 people that is
Incidence = new cases / total population
Incidence = 200/ 1000 over two year period
The incidence rate is now 10 cases per 1000 people as the incidence proportion 200 per 1000 is divided by the number of years and that in this case is 2.
In statistics, the incidence rate is referred to as the rate of occurrence within a population at a particular time.
In market research, the incidence rate is referred to as the frequency of occurrence or the number of people shown in percentage that is eligible to take part in a study. Suppose market research is looking to target only men, then the incidence rate drops from 100% to 50% immediately. The number of people involved in the sample pool will further drop if you further target men who are married. In this scenario, the incidence rate will drop and become less than the estimated 50%. Similarly, if you target married men with children, the incidence rate will again dip.
Online companies also take the help of incidence rates to get an estimate about the number of respondents who will be a part of the sample pool and qualify for the study. It is the fact that the low incidence rate leads to extra work to collect completes, the additional cost per complete and a higher expense of the overall project.
Why and how does incidence rate drive research costs?
One of the essential factors that have a direct impact on the cost of doing market research is the ease with which the organizations get hold of its qualified respondents and persuade them to complete the survey. The fact is that the difficulty one faces in reaching the target respondents results in a time-consuming process and this results in more costs for the research project.
When an organization plans market research, it will first get an estimate about the number of individuals who when invited, will either decline to become a part of the survey and will not qualify for it. This estimate is essential as it acts as a guiding force in estimating the cost of the project.
The quality and source of a contact list have a direct impact on the incidence rate because the rate is better only when the listing is better and clearly defined. How specific a target audience is, in likelihood, has an impact on the cost. For instance, if an organization has a particular audience in mind, then the incidence rate will be lower.
Broader specification means low effort levels in acquiring completed surveys, low cost per completed survey and thus higher incidence rate. Stringent qualifications or specifications mean more significant effort in learning complete reviews, the high price per comprehensive study and low incidence rate. It is a fact that even a slight difference in percentage points in incidence rate could result in a high percentage increase in costs in the market research.
Some other factors that have an impact on the incidence rate estimates are the length of the survey and the method of collecting the required data and information via mail, email, phone, etc. It is the research team that determines the necessary fielding resources, design elements and likely timing to create a realistic schedule, budget and approach so that it becomes easier to design the sample design with reasonable incidence rates that can meet the necessary budget requirements.
Most of the organizations calculate the incidence rate for every study they undertake. With the help of available data and information, it becomes easier to compare incidence rates for earlier studies or surveys that have some similarities to the one they are undertaking at present.
Examples of incidence rate
The incidence rate can be explained in simple terms with the help of a case. An organization is conducting a customer satisfaction survey with the help of the current customer list. Some of the phone numbers on that list are not working and the list might also include some incorrect email addresses.
In spite of it, the list is qualified as it is of the current customers. In such a case, the cost per survey that has been completed will be low and the incidence rate will be higher.
Types of incidence rate
In the market research, the incidence rate is referred to as the percentage of people in a sample study or the number of people the survey or study was sent to or the number of respondents that qualify for the study. The two types of incidence rate are as follows-
1. Predicted IR or incidence rate
The predicted IR is about the estimated respondents that have a chance to qualify for a study that has been based on the required and screened data. It fluctuates throughout the field time and helps the organization or the team to assume the number of respondents that should be sent during, before and to the study or survey.
2. Actual IR or incidence rate
The actual IR is about the actual number of respondents that have qualified for the study or survey. It was based on the final number of respondents whom the study was sent.
Importance of the incidence rate
The importance of incidence rates are described below-
- It is imperative to understand the incidence rate as it is the guiding force behind several decisions like which sample pool or panel provider should be used.
- The incidence rate helps in identifying the errors that can occur in the survey or the study
- It can easily anticipate the timing for example if the actual incidence rate is less than the predicted incidence rate then it means that either the timing will have to be extended or the screening criteria will have to be changed to allow several respondents to qualify for the study. if the actual incidence rate is more than the predicted incidence rate, then it means that the project will close sooner than the original estimate
- The incidence rate has an impact on the feasibility in market research and is an essential tool for panel providers