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In descriptive statistics, a **decile** is any of the nine values that divide the sorted data into ten equal parts, so that each part represents 1/10 of the sample or population.^{ [1] } A decile is one possible form of a quantile; others include the quartile and percentile.^{ [2] } A decile rank arranges the data in order from lowest to highest and is done on a scale of one to ten where each successive number corresponds to an increase of 10 percentage points.

The **median** is the value separating the higher half from the lower half of a data sample. For a data set, it may be thought of as the "middle" value. For example, in the data set [1, 3, 3, 6, 7, 8, 9], the median is 6, the fourth largest, and also the fourth smallest, number in the sample. For a continuous probability distribution, the median is the value such that a number is equally likely to fall above or below it.

In statistics and probability **quantiles** are cut points dividing the range of a probability distribution into continuous intervals with equal probabilities, or dividing the observations in a sample in the same way. There is one fewer quantile than the number of groups created. Thus quartiles are the three cut points that will divide a dataset into four equal-sized groups. Common quantiles have special names: for instance quartile, decile. The groups created are termed halves, thirds, quarters, etc., though sometimes the terms for the quantile are used for the groups created, rather than for the cut points.

**Statistics** is the discipline that concerns the collection, organization, displaying, analysis, interpretation and presentation of data. In applying statistics to a scientific, industrial, or social problem, it is conventional to begin with a statistical population or a statistical model to be studied. Populations can be diverse groups of people or objects such as "all people living in a country" or "every atom composing a crystal". Statistics deals with every aspect of data, including the planning of data collection in terms of the design of surveys and experiments. See glossary of probability and statistics.

In statistics, quality assurance, and survey methodology, **sampling** is the selection of a subset of individuals from within a statistical population to estimate characteristics of the whole population. Statisticians attempt for the samples to represent the population in question. Two advantages of sampling are lower cost and faster data collection than measuring the entire population.

**Mortality rate**, or **death rate**, is a measure of the number of deaths in a particular population, scaled to the size of that population, per unit of time. Mortality rate is typically expressed in units of deaths per 1,000 individuals per year; thus, a mortality rate of 9.5 in a population of 1,000 would mean 9.5 deaths per year in that entire population, or 0.95% out of the total. It is distinct from "morbidity", which is either the prevalence or incidence of a disease, and also from the incidence rate.

A **percentile** is a measure used in statistics indicating the value below which a given percentage of observations in a group of observations falls. For example, the 20th percentile is the value below which 20% of the observations may be found.

In statistics, **exploratory data analysis** (**EDA**) is an approach to analyzing data sets to summarize their main characteristics, often with visual methods. A statistical model can be used or not, but primarily EDA is for seeing what the data can tell us beyond the formal modeling or hypothesis testing task. Exploratory data analysis was promoted by John Tukey to encourage statisticians to explore the data, and possibly formulate hypotheses that could lead to new data collection and experiments. EDA is different from initial data analysis (IDA), which focuses more narrowly on checking assumptions required for model fitting and hypothesis testing, and handling missing values and making transformations of variables as needed. EDA encompasses IDA.

**Dargaville** is a town in the North Island of New Zealand. It is situated on the bank of the Northern Wairoa River in the Northland region. The town is located 55 kilometres southwest of Whangarei.

The **Friedman test** is a non-parametric statistical test developed by Milton Friedman. Similar to the parametric repeated measures ANOVA, it is used to detect differences in treatments across multiple test attempts. The procedure involves ranking each row together, then considering the values of ranks by columns. Applicable to complete block designs, it is thus a special case of the Durbin test.

In statistics, **resampling** is any of a variety of methods for doing one of the following:

- Estimating the precision of sample statistics by using subsets of available data (
**jackknifing**) or drawing randomly with replacement from a set of data points (**bootstrapping**) - Exchanging labels on data points when performing significance tests
- Validating models by using random subsets

In statistics, a **Q–Q (quantile-quantile) plot** is a probability plot, which is a graphical method for comparing two probability distributions by plotting their quantiles against each other. First, the set of intervals for the quantiles is chosen. A point (*x*, *y*) on the plot corresponds to one of the quantiles of the second distribution plotted against the same quantile of the first distribution. Thus the line is a parametric curve with the parameter which is the number of the interval for the quantile.

The **National Census of 2001** was the 2nd comprehensive national census of the Republic of South Africa, or Post-Apartheid South Africa. It undertook to enumerate every person present in South Africa on the census night between 9–10 October 2001 at a cost of R987,000,000.

**Advanced Placement Statistics** is a college-level high school statistics course offered in the United States through the College Board's Advanced Placement program. This course is equivalent to a one semester, non-calculus-based introductory college statistics course and is normally offered to juniors and seniors in high school.

The **YO postcode area**, also known as the **York postcode area**, is a group of 30 postcode districts for post towns York, Bridlington, Driffield, Filey, Malton, Pickering, Scarborough, Selby, Thirsk, and Whitby in Yorkshire, England.

In engineering, science, and statistics, **replication** is the repetition of an experimental condition so that the variability associated with the phenomenon can be estimated. ASTM, in standard E1847, defines replication as "the repetition of the set of all the treatment combinations to be compared in an experiment. Each of the repetitions is called a **replicate**."

In descriptive statistics, the **seven-number summary** is a collection of seven summary statistics, and is an extension of the five-number summary. There are two similar, common forms.

In statistics, the **interdecile range** is the difference between the first and the ninth deciles. The interdecile range is a measure of statistical dispersion of the values in a set of data, similar to the range and the interquartile range, and can be computed from the (non-parametric) seven-number summary.

In the New Zealand education system, **decile** is a key measure of socioeconomic status used to target funding and support schools. In academic contexts the full term "**socioeconomic decile**" or "**socioeconomic decile band**" may be used.

The **Hosmer–Lemeshow test** is a statistical test for goodness of fit for logistic regression models. It is used frequently in risk prediction models. The test assesses whether or not the observed event rates match expected event rates in subgroups of the model population. The Hosmer–Lemeshow test specifically identifies subgroups as the deciles of fitted risk values. Models for which expected and observed event rates in subgroups are similar are called well calibrated.

- ↑ Lockhart, Robert S. (1998),
*Introduction to Statistics and Data Analysis: For the Behavioral Sciences*, Macmillan, p. 78, ISBN 9780716729747 . - ↑ Sheskin, David J. (2003),
*Handbook of Parametric and Nonparametric Statistical Procedures*(3rd ed.), CRC Press, p. 10, ISBN 9781420036268 .

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