Concepts inWhen is query performance prediction effective?
Prediction
A prediction or forecast is a statement about the way things will happen in the future, often but not always based on experience or knowledge. While there is much overlap between prediction and forecast, a prediction may be a statement that some outcome is expected, while a forecast may cover a range of possible outcomes. Although guaranteed information about the information is in many cases impossible, prediction is necessary to allow plans to be made about possible developments; Howard H.
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Performance prediction
In computer science, performance prediction means to estimate the execution time or other performance factors (such as cache misses) of a program on a given computer. It is being widely used for computer architects to evaluate new computer designs, for compiler writers to explore new optimizations, and also for advanced developers to tune their programs. There are many approaches to predict program 's performance on computers.
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Kendall tau rank correlation coefficient
In statistics, the Kendall rank correlation coefficient, commonly referred to as Kendall's tau (¿) coefficient, is a statistic used to measure the association between two measured quantities. A tau test is a non-parametric hypothesis test which uses the coefficient to test for statistical dependence. Specifically, it is a measure of rank correlation: that is, the similarity of the orderings of the data when ranked by each of the quantities.
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Tau
Tau is the 19th letter of the Greek alphabet. In the system of Greek numerals it has a value of 300. The name in English is pronounced . This is because the pronunciation of the combination of Greek letters ¿¿ has changed from ancient to modern times from one of [au au] to either [av av] or [af af], depending on what follows. Tau was derived from the Phoenician letter taw . Letters that arose from tau include Roman T and Cyrillic Te (¿, ¿).
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Coefficient
In mathematics, a coefficient is a multiplicative factor in some term of an expression (or of a series); it is usually a number, but in any case does not involve any variables of the expression. For instance in the first three terms respectively have the coefficients 7, ¿3, and 1.5 (in the third term the variables are hidden, so the coefficient is the term itself; it is called the constant term or constant coefficient of this expression).
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Utility
In economics, utility is a representation of preferences over some set of goods and services. Preferences have a utility representation so long as they are transitive, complete, and continuous. Utility is usually applied by economists in such constructs as the indifference curve, which plot the combination of commodities that an individual or a society would accept to maintain a given level of satisfaction.
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