








Chance variation, chance error
Glossary of Statistical Terms 
A random variable can be decomposed into a sum of its expected value and chance variation around its expected value. the expected value of the chance variation is zero; the standard error of the chance variation is the same as the standard error of the random variable—the size of a "typical" difference between the random variable and its expected value. see also sampling error.


Decomposed, английский
Difference, английский
 Disagreement, inequity, contrast, dissimilarity, incompatibility
 Разница; разность
 An important army term, meaning firstly the sum to be paid by officers when exchanging from the half to full pay; and, secondly, the price or difference in value of the several commissions.

Random variable, английский
 A random variable is an assignment of numbers to possible outcomes of a random experiment. for example, consider tossing three coins. the number of heads showing when the coins land is a random variable: it assigns the number 0 to the outcome {t, t, t}, the number 1 to the outcome {t, t, h}, the number 2 to the outcome {t, h, h}, and the number 3 to the outcome {h, h, h}.
 Случайная переменная
 A function that assigns a real number to each and every possible outcome of a random experiment.
Quota sample, английский
A quota sample is a sample picked to match the population with respect to some summary characteristics. it is not a random sample. for example, in an opinion poll, one might select a sample so that the proportions of various ethnicities in the sample match the proportions of ethnicities in the overall population from which the sample is drawn. matching on summary statistics does not guarantee that the sample comes close to matching the population with respect to the quantity of interest. as a result, quota samples are typically biased, and the size of the bias is generally impossible to determine unless the result can be compared with a known result for the whole population or for a random sample. moreover, with a quota sample, it is impossible to quantify how representative of the population a quota sample is likely to be—quota sampling does not allow one to quantify the likely size of sampling error. quota samples are to be avoided, and results based on quota samples are to be viewed with suspicion. see also convenience sample.






