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In statistical process control (SPC), the ¯ and R chart is a type of scheme, popularly known as control chart, used to monitor the mean and range of a normally distributed variables simultaneously, when samples are collected at regular intervals from a business or industrial process. [1]
This means that most men (about 68%, assuming a normal distribution) have a height within 3 inches of the mean (66–72 inches) – one standard deviation – and almost all men (about 95%) have a height within 6 inches of the mean (63–75 inches) – two standard deviations. If the standard deviation were zero, then all men would share an ...
Conversely, if is a normal deviate with parameters and , then this distribution can be re-scaled and shifted via the formula = / to convert it to the standard normal distribution. This variate is also called the standardized form of X {\textstyle X} .
In descriptive statistics, the range of a set of data is size of the narrowest interval which contains all the data. It is calculated as the difference between the largest and smallest values (also known as the sample maximum and minimum). [1] It is expressed in the same units as the data. The range provides an indication of statistical ...
The "chart" actually consists of a pair of charts: one, the individuals chart, displays the individual measured values; the other, the moving range chart, displays the difference from one point to the next.
This can be generalized to restrict the range of values in the dataset between any arbitrary points and , using for example ′ = + (). Note that some other ratios, such as the variance-to-mean ratio ( σ 2 μ ) {\textstyle \left({\frac {\sigma ^{2}}{\mu }}\right)} , are also done for normalization, but are not nondimensional: the units do not ...
In a histogram, each bin is for a different range of values, so altogether the histogram illustrates the distribution of values. But in a bar chart, each bar is for a different category of observations (e.g., each bar might be for a different population), so altogether the bar chart can be used to compare different categories.
The standard definition of a reference range for a particular measurement is defined as the interval between which 95% of values of a reference population fall into, in such a way that 2.5% of the time a value will be less than the lower limit of this interval, and 2.5% of the time it will be larger than the upper limit of this interval, whatever the distribution of these values.