I was answering a question today and it reminded me of a discussion I had with a couple colleagues about the optimal amount of choices in a Likert scale. I vouched for the classic 5, one of us stood for 10 and the third person liked a variable approach where 10 options should be used for in depth research with a great deal of fine tuning while fewer choices should be used on superficial research and the extremes of age targets (younger - older). Nevertheless, while I could see some logic in the second guy's approach, it didn't convince me at 100%, maybe because I'd only use a Likert scale if I can't use a Semantic Differential Scale.
Now I'm working with a behavioral psychologist and the first test she did used a Likert Scale with 5 choices. I asked about the number of choices and she told me you can use a variable number of choices, but in the end, when translated to a mathematical matrix, it returns more or less the same median, variance and kurtosis.
However, I'd never pass on a chance of knowing a better way to use a tool, so, In short, my questions are:
- are there any studies that unequivocally demonstrate the optimal number of choices in a Likert scale?
- assuming "variable" is the correct answer, are there any tools or guidelines that allow the researcher to define this optimal number?
- is it correct that 5,7 or 9 options will provide more or less the sam results? Or more choices equal more fine tuning
Please notice I already know about the different theories defending what my colleagues stood for, I'm probably looking for an answer involving maths or some kind of function that statistically shows the answer is correct in as many different scenarios as possible