The answer depends on what "profitability sampling" means. Despite an MSc degree in statistics and 30 years' experience as a statistician, I have not come across the term!
it is prefered
sampling theorem is defined as , the sampling frequency should be greater than or equal to 2*maximum frequency, and the frequency should be bounded.. i,e fs=2*fmax where fs= sampling frequency
Chorionic villus sampling is best performed between 10 and 12 weeks of pregnancy
Chorionic villus sampling is not recommended for women who have vaginal bleeding or spotting during the pregnancy
The Nyquist Therorem states that the lowest sampling rate has to be equil to or greather than 2 times the highest frequency. Therefore the sampling rate should be 400Hz or more.
Dexron 3 is prefered.
The Nyquist Theorem says that the sampling frequency should be twice the bandwidth to avoid aliasing. Thus if the bandwidth of the system is bw then the sampling frequency f=2*bw.
sample design
In a stratified sample, the sampling proportion is the same for each stratum. In a random sample it should be but, due to randomness, need not be.
yes
Your groups should be mutually exclusive and collectively exhaustive.
The rule of thumb is: Prefered is Four seconds, Minimum 2 seconds. If you are texting: Prefered 4 Hours Minimum 2 hours