# IAS: Statistics Glossary R to Z

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## Statistics Glossary: R to Z

- Random Error: Error that occur as a result of sampling variability.
- Random Sampling: It is the selection of individuals from the population in such a way that each individual of the population has the same chance of being selected i.e.. . a sample so selected must be a true representative of its population. This process of sampling is called random sampling.
- Range: The difference between the largest and the smallest value of a set.
- Region of acceptance: It is the area under a probability curve, in which a computed test statistics will lead to the acceptance of the null hypothesis.
- Region of Rejection: Area under the probability (normal) curve in which a computed test statistics will lead to the rejection of the null hypothesis.
- Regression: The estimation of the linear dependent of one or more independent variables on a dependent variable.
- Relative frequency: The ratio of a class frequency to the total frequency.
- Research Hypothesis: The expectation or prediction, that is to be tested by a researchers.
- Residual: The vertical distance (deviation) between a pre-assigned value of y and its actual value.
- Sample: A finite set of objects, drawn from the population with the aim that it represents the population.
- Sampling Distribution: The distribution obtained by computing a statistic for a large number of sample drawn from the same sample population.
- Scatter Diagram: If a graphic display used to explain the degree of correlation between two variables, by the means of points or dots.
- Skewed: A distribution displayed at one end of the scale with its tail strung out at the other end.
- Standard-Deviation: It is the square root of the arithmetic mean of the square of deviations of various values from their arithmetic mean.
- Standard error: A measure of variation in random of a statistic standardize the conversion into a z-score.
- Statistical Significance: The probability of obtaining a given result by chance.
- Sample space: The totality of all outcomes as a result of a random experiment.
- Statistic: It is a branch of mathematics that describes the aggregate of facts, affected to a marked extent by multiplicity of causes, numerically expressed, in numerated as estimated according to reasonable standard accuracy, collected in a systematic manner for a pre-determined purpose and placed in a relationship to each other.
- Symmetric: A shape in which one side is the mirror image of other.
- Systematic Error: The consistency in under-estimating or over-estimating a true value.
- T-Distribution: A probability distribution used when the standard deviation of the population is unknown and the sample size is small.
- Test statistic: A computed statistic value used to decide a hypothesis test.
- Two-Tail-Test: A state of predictions that indicate whether the two values are equal or not equal.
- Type-I-Error (a Error) : Rejecting a null-hypothesis when it is true.
- Type-II-Error (b Error) : Failing to reject the null-hypothesis when it is false.
- Trial: A procedure or an experiment to collect any statistical data.
- Upper Quartile (Q3) : The 75
^{th}percentile of the set of observation. - Unbiased Estimator: The expected value of statistic which is equal to the corresponding population parameter.
- Variable: As observed characteristic of phenomenon which is to be studied.
- Variance: The square of the standard deviation of the score about the mean distribution.
- Z-score: The standardized normal variates which are obtained by subtracting the mean and dividing by the standard deviation.