Enter an observed survey mean, drag the response-rate slider, and watch the worst-case identified interval sweep wider or narrower in real time - the core intuition behind nonresponse-bias sensitivity analysis, no dataset upload, no R. A second calculator answers the classroom follow-up: "what response rate would I need to trust this effect?"
Enter the same respondent mean and scale bounds, plus a threshold you want the true population value to clearly beat (e.g. a comparison group's rate, a pass/fail cutoff, "50%"). This finds the minimum response rate at which even the worst-case bound still clears that threshold - below it, nonresponse alone could explain away the result.