There are sample size calculators for MVT experiments of conversion rates.
But how to calculate it in case response is a scale data and is given by each user (like survey data)?
I am working on multivariate testing (DoE) of a prototype. I want to use UX(usability) metrics as outputs in user testing.
Metrics are scale ratings (1 to 10) that each user provides and continuous data such as time on task.
It is 2 level Definitive design. I want to see minimal effect of 20% and I can guess variance only from similar studies.
I can use G-power, SAS JMP or some online calculator.