Instead of relying on the sorts of people who can be persuaded to pick up a landline telephone or put themselves forward for an internet panel, the BES survey knocked on doors selected by a genuinely random sampling.
Sturgis explains that by using genuinely random sampling, "in which everybody has at least some chance of being asked to take part in the survey", the BES study sets a gold standard, against which the shortcomings of both telephone and online polling can be judged.
The ROC curve is a plot of the sensitivity (genuinely positive samples that are detected as positive, "true positives") against 1 - specificity (negative samples that are detected as positive, "false positives") for different cutoff points [ 4].
This suggests that the BES survey did a better job than all the pre-election phone and online polls of building a genuinely representative sample.
My unscientific (because untestable) hypothesis is that it is getting increasingly hard, verging on impossible, to muster any genuinely representative sample of our Internet-fragmented and increasingly internalized society.
We accept that while snowballing may not lead to a genuinely representative sample, it remains the most pragmatic and cost-effective method for case-detection in low resource settings [22].
But efforts were made to make the country samples genuinely comparable (ie, the British sample isn't entirely accountants, the Spanish sample builders, the German group engineers).
Such data-derived modelling is the preferred method of estimating and comparing screening performance because it can be based on a large enough sample to provide the necessary precision, the sample genuinely represents the population at large, and there are no missing values, with complete ascertainment of clinical events.
Real-time qPCR inhibition can indeed be muted and even eliminated merely by RNA sample dilution in most cases, therefore leaving all nucleic acid target templates within each RNA sample genuinely available to participate in highly efficient (and-therefore-quantitatively-accurate) qPCR amplifications.
This approach assumes that cases where individual reads from a sample genuinely map to three or more distinct locations in the reference genome will be extremely rare, which will generally be true for short-read data from samples that have not greatly diverged from the reference genome.
For example, single-nucleotide polymorphism (SNP) samples, being genuinely discrete, can be immediately utilized.
