He explained that there was "no single, straightforward fix for not having the right sort of people in your sample".
You found that about 10 percent of the tweets in your sample had emoticons in them.
But ask a sampling of Time Warner observers, everyone from investors to analysts to other media executives, what Mr. Bewkes's strategy should be, and you will likely get as many different answers as there are people in your sample.
Such errors come from inadvertently designing your study in such a way that you get too many of some kind of person in your sample.
In any case, there are not enough past housing data to form a rich statistical picture of the market especially if you decide not to include the 1930s nationwide fall in house prices in your sample.Neither could the models take account of falling mortgage-underwriting standards.
"If you do an experiment on Facebook, you've got half a billion people in your sample," says Prof Robinson.
"A big problem with mass spec in general is normalization of data across time on the same mass spec, across different machines, across different labs, so having reference standards that contain all of the compounds that are in your samples is really helpful and can increase the precision of the data a lot," says Welti.
For observed drug tests, dropping an oxidizer in your sample or emptying a vial of urine taped to the inside of your thigh won't do.
The theory is simple: Every person in the population you want to sample has the same chance of being interviewed, which means that if you are surveying American adults, every single person in the U.S. over age 18 has the same probability of being included in your sample.
Add all the numbers in your sample together.
