What is sampling rate in Statistics? I came across the term "sampling rate" but really know nothing about it. I only know participation rate in statistics or research. And in my searches in google for "sampling rate", they usually relate it to physics and waves. But what does it mean in statistics?
 A: Sampling rate is often described in the context of signal processing as the number of samples per time. Less frequently, you'll see the term in non-temporal domains to describe the number of samples per X. I'll focus on these non-temporal applications of the term "rate".
The sampling rate can be defined as the proportion of a population that is sampled. If you have 100 people in a cohort, and sample 40 of them, your sampling rate is 40%. Usually, the absolute number of samples will be more important than the proportion of the population that's sampled, but the sampling rate can be useful in allocating your sample among different subgroups. If you have subgroups of different variability, it can be useful to adjust the sampling rate among subgroups. You can imagine a cohort of 100 patients, 50 of which are healthy and all very similar, and 50 of which have a disease and are very heterogeneous. To get the most precise estimate of a mean value in the whole cohort, you should increase the sampling rate in your high-variance group, and decrease the sampling rate in your low-variance group.
Here's an example of the term sampling rate being used to describe the fraction of samples taken from a larger population.
A: Sampling rate is the same as sampling frequency. How frequent you sample.
Say 20 times in a minute or 3 times daily.
The sampling rate is something that should be regular thus it can be not so regular, or even irregular in which case we speak of average sampling rate.
Check also what is sampling.
