Constant Sum Scales, also known as Allocation Scales or 100-point Scales, are a type of rating scale used in research to measure the relative importance, allocation, or distribution of resources, preferences, or opinions across multiple items or attributes. Unlike Likert scales or Semantic Differential Scales that use fixed response options, Constant Sum Scales allow respondents to allocate a fixed sum of points or percentages among different options or attributes based on their perceived importance or preference.
Key features of Constant Sum Scales include:
1. Fixed Sum: Respondents are provided with a fixed sum of points or percentages, such as 100 points or 100%, which they must allocate across multiple items or attributes.
2. Allocation of Points: Participants distribute or allocate their points or percentages among the items or attributes based on their judgment of their relative importance, preference, or distribution.
3. Flexibility: Constant Sum Scales provide flexibility, allowing respondents to allocate points or percentages unevenly among the items, indicating their relative priority or preference.
4. Quantitative Representation: The allocation of points or percentages provides a quantitative representation of respondents' opinions, preferences, or resource allocation.
Example of a Constant Sum Scale measuring preferences for food items:
Burger: [__%]
Pizza: [__%]
Salad: [__%]
Sushi: [__%]
In this example, respondents are given 100% to distribute among four food items based on their preferences. They allocate the percentages according to their perceived importance or preference for each food item.
Constant Sum Scales offer several advantages in research:
• Flexibility: Respondents can express nuanced preferences or allocate resources based on their individual judgments.
• Relative Importance: The scale allows for the assessment of the relative importance or priority of different items or attributes.
• Quantitative Data: The allocation of points or percentages generates quantitative data that can be analyzed and compared across respondents.
However, it is important to consider some limitations:
• Subjectivity: Respondents' allocations may be influenced by personal biases, varying interpretations of importance, or cognitive biases.
• Complexity: Constant Sum Scales may require more cognitive effort and numeracy skills from respondents compared to other rating scales.
• Interpretation: The interpretation of results may depend on the specific context, instructions, and scale design. Researchers should carefully define and communicate the purpose and instructions for allocating the points or percentages.
Constant Sum Scales can be used in various research contexts, such as measuring preferences, resource allocation, or importance ratings across multiple items or attributes. They provide a flexible and quantitative approach to capturing individuals' relative judgments and distributions.
