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How to appropriately use interval scales in your survey questions?

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What is an Interval Scale?

An interval scale can be defined as a quantitative measurement scale where variables have an order, the difference between two variables is equal, and the presence of zero is arbitrary. It can be used to measure variables that exist along a common scale in equal intervals.

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Interval Scales

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Interval Scale vs Other Measurement Scales

There are four fundamental levels of quantitative measurement scales:

  1. Nominal
  2. Ordinal
  3. Interval
  4. Ratio

Nominal scales involve variables that are simply named but have no specific order or defined interval. 

On the other hand, Ordinal scales do have an order, but the difference between the two variables is not defined. In Interval scales, there is order and a defined distance between variables.

The final scale, known as the Ratio scale, produces the order of variables, the difference between variables, and (unlike the Interval scale) also provides information on the value of true zero

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How is an Interval Scale used in Surveys?

Interval scales are best suited in surveys where respondents must enter values regarding temperature, time, and dates. Interval scales can be easily integrated into multiple choice questions or rating scale questions by asking respondents to use a numerical scale to make a rating.


Example of Interval Scale

A popular example of the use of Interval scales within surveys is within NPS surveys. Net Promoter Score surveys measure the likelihood of customers recommending a company’s products or services to others. It does so by asking them to rate their likelihood to do so on a numeric scale from 0 to 10, where 0 indicates they are not likely at all, and 10 indicates they are very likely.

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Characteristics of an Interval Scale

These are a few characteristics of an interval scale: 

  1. Values between two variables can be subtracted to define the difference between two variables.
  2. Interval scales allow you to calculate the mean and median of variables.
  3. Interval Scales are preferred in statistics as numerical values may be assigned to arbitrary assessments such as those of opinions and feelings.
  4. Interval data is useful in business and scientific analysis as it is quantitative, and straightforward. 
  5. Nominal scales and Ordinal scales do not provide as much information as Interval scales, as they are qualitative in nature and do not provide information on the difference between two variables.

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How do you Interpret Interval Scale Results

Certain survey questions, such as those used in NPS and CSAT surveys, have specific methods and formulas for interpreting their results.

Interval scales may not always help generate useful data, especially if the measurement system used is highly arbitrary. However, they may be used to calculate the mean and median values of a set of aggregate data.

The more arbitrary your interval scale is, the less useful the data produced by it will be. Although a constant interval variable is necessary to interval scales, it may be difficult to keep the interval variable constant while measuring variables such as opinions and feelings. Most interval scales, even those widely used, tend to have only modest accuracy and are not fully reliable. 

When appropriately used, interval scales can be used to extract useful and powerful data from survey responses as it can add mathematical significance to quantify opinion and feedback surveys. 

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Why Choose Voxco?

These are a few reasons you should choose Voxco for your survey software needs:

  • Use any kind of Scale

While creating surveys with Voxco, you can use any kind of scale, whether that be nominal, ordinal, interval, or ratio. 

  • Access to Dynamic Dashboards

Voxco’s powerful dashboards analyse survey responses as and when they come in. With our dashboard, Interval data can be measured and analyzed in the most efficient way.  

  • Wide range of Survey Templates

Voxco survey software has survey templates ready for any kind of survey you may need. Our NPS, CSAT, and CES survey templates can be used to make your surveying process quick and easy as our software analyses the responses for you. 

  • Centralised Survey Authoring

 With Voxco, you can create your survey once and send it to respondents across all channels. This saves time as it eliminates the need for the reprogramming of the same questionnaire.

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Hindol Basu 
GM, Voxco Intelligence


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