I have yet to hear any reasonable theoretical justification for the calculation of sampling error with a convenience sample".
I have yet to hear any reasonable theoretical justification for the calculation of sampling error with a convenience sample". The argument for using the margin of error with Internet surveys is that even nonrandom-sample surveys have sampling variability that is largely random and predictable.
Is there any justification for such a calculation?
(While the thermodynamic justification for these latter calculations is straightforward, it is a somewhat novel approach to calculating the optimal length and thus worth testing by independent calculations).
As such, given that 1) vitamin D deficiency is the norm in hemodialysis patients, 2) vitamin D downregulates the renin-angiotensin system [ 24, 25, 35], and 3) increased RAS activity is associated with alterations in cardiac autonomic tone [ 35- 37], we feel there is sufficient justification for the sample size calculation herein.
Furthermore, the relatively small population size, lack of power calculations, and justification for the sample size also limit generalizability of these results.
This is an important observation and it will be used as justification for the methodology employed in the calculations in the companion paper which proceeds to simulate fully developed, three-dimensional fluidized granular flows in a rectangular channel.
More than half of the research protocols provided no justification for the assumptions used in the sample size calculation.
Unfortunately, our results suggest the concept of sample size calculations seems to be almost unknown in psychiatric research outside the field of clinical trials; less than 4%% of the evaluated articles included sample size calculations, power analysis or any other justification for the sample size.
Papers did not state that a power calculation had been undertaken nor give any justification for the numbers of participants needed to detect an effect of differences in fruit and vegetable intake and the incidence of type 2 diabetes.
In this survey, 30% (14 50%) of the RCTs gave no such calculation and 19% (7 39%) of them provided no justification for the sample size in the methods section.
