For an unknown population frame Creative Research gives a formula for computing a sample size. Now after knowing the size, What sampling method?

What kind of fluid could I use for a pitfall trap that also does not invalidate molecular testing?

Hi, I want to start testing pitfall trap to obtain ants samples, but I need to conduct molecular analysis on those insects. So, what kind of fluid can I use? Ethanol expires too early and I need...

03 March 2021 5,978 5 View

How optimize the Size Exclusion Chromatography?

Hello! I'll do a size exclusion chromatography, but I only have an open column, and I'll perform the peptide extraction from yeast, using buffer lysis (sodium phosphate 50 mM/NaCl 30 mM/DNAse and...

01 March 2021 2,215 2 View

Would fecal samples stored at -20C for over a year impact metagenomic analysis?

Dear All, I have access to some rodent fecal samples that have been stored at -20C instead of -80C. Anyone have experience with the impact of stowage condition on comparative metagenomic analysis...

01 March 2021 2,512 1 View

No title

01 March 2021 3,905 5 View

What test should I use to compare two or three means, if data is not normally distributed but sample size is > 30 in each group?

I personally feel this as a most confusing question. As per my understanding, if sample size is > 30, and sample is skewed, we can still use paramteric approach, as it will follow Z...

01 March 2021 1,587 6 View

Is it necessary to report effect size (ES) in statistics of biomedical research given that we already report p values routinely?

Pls share your thoughts

01 March 2021 7,330 4 View

Does different dilution factors affect negatively on NH3 reading ?

I have a sample of treated water sample & asked to obtain ammonia conc. in sample using a machine with 5-25 ppm detection range. However, upon testing with different dilution factors, all...

27 February 2021 8,483 3 View

How to compare 2 samples recruited with different sampling methods?

If I want to compare characteristics of 2 groups of patients, one group is recruited from a random sample of the general public while another group is from a sample with a fixed gender (male to...

26 February 2021 3,526 3 View

Can random sampling have inclusion criteria?

As random sampling means that everyone in the population have an equal chance to be chosen, can it have inclusion criteria? My research participants have been chosen based on the inclusion...

26 February 2021 6,905 10 View

Why there are two peaks while using the mie plot of Silver nanoparticle?

Hi, I am trying to learn the theoretical modelling of silver nanoparticle using the Mie scattering theory. After that, I discovered a software named Mieplot developed by Philip Laven, where it...

25 February 2021 7,493 6 View

Jawad Abbas

For unknown population size, convenience sampling is preferable. This is best approach of non-probability sampling when you cannot proactively seek out subjects.

James E. McLean

You will need to determine your sampling method before determining your sample size. That is because the precision of your estimates for each cluster, strata, or stage determines the overall accuracy of your estimations or comparisons. One you determine the units you will be sampling in the specific clusters, stratification, stage, etc., the sample size determination becomes much simpler as you can determine the sample size for each component and add them together.

Mariano Ruiz Espejo

I agree with James. The most simple sampling method is "simple random sampling with replacement" in which, in each selection of unit, all the population units have the same probability of being selected, 1/N. And each selection is independent of the others.