I was wondering how to identify bad/random respondents for my CBC experiment (including 2 CBC exercises and some demographic questions). I have read about RLH, completion time and straightliners, but I am not really sure how to use these criteria in practice.

- How should you compute RLH? I understand how you can compute the median, but I am not sure about the calculation of the 95% percentile and whether you should exclude or include respondents below that RLH. And should you use both the median and the 95% percentile RLH, or one of them?

Also, I have 2 CBC exercises. So should I do the HB analysis to get the RLH for both exercises separately (for both the random respondents and my own data), and then calculate the median/95% percentile RLH for both exercises separately (with the random respondents data) and use the calculated numbers for my HB analysis of my 2 exercises separately (comparing it to my own data)? Or should I first combine the 2 exercises and then calculate the RLH on the random respondents with an HB analysis of both exercises at the same time? (If so, the latter, how could I do that?)

- What would you say is a 'fast completion time'? Is there any rule for that?

- Should you look the straightliners up by yourself or is there any tool to easily see which respondents are straightliners?

Are there any more criteria to identify these bad respondents?

Thanks in advance!

Regarding speeders: In other posts I read about 40% or 50% faster than the median survey time. There is no rule for that, it is up to you to define that. But this should be a good rule of thumb

Straightliners: I guess this is totally depending on your context. In your study you might include something like contradicting questions (not obvious) as a test, and if people fail, you can exclude them.