A constant sum question is used in market research surveys in which respondents can allocate the number of points on the specified criteria or options. The total of these points can be defined by the survey creator while designing the survey which will be the maximum points available to the respondents while answering this question. Constant sum question type gives an understanding of how respondents value each answer option. If customers feel that certain features of a product or service are more important than others, they will give more points to those features.
Constant sum scale is a great way to create differentiation among data set. It helps you find out which factors are important and which are not for respondents. They are especially helpful in cases where many factors are critical and overlap in some sense. Other question types such as likert scale can find out what matters most to the respondents, but they can't highlight the variance factor.
You can ask respondents to allocate 100 points on how they spend their income. Give them options and ask to assign points in order of importance. Say, they spend $40 on groceries, $20 on entertainment, $30 on utilities and $10 for miscellaneous expenses. Thus, you can find out groceries is the most important expense for the respondents followed by the utilities.
Constant sum question can be used while calculating percentages, school assignments, finances, understanding customer choices, etc. This type of question is useful when you want to understand how respondents allocate points to each answer item. You can also find out to what extent do they give importance to the answer choices.
With rank order questions too, you can find out the order in which respondents consider the answer options as important to them. However, you cannot know the extent to which an answer option is important. With the constant sum scale in survey, you can find the relative weight given to the options.
A constant sum question permits the collection of ratio data, i.e., the weight of various options in the total sum of 100. You can also find out the ratio of various options and the importance they hold relative to each other.
Check out our constant sum question help document for a better understanding of how it works.