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  2. Frequency (statistics) - Wikipedia

    en.wikipedia.org/wiki/Frequency_(statistics)

    A frequency distribution table is an arrangement of the values that one or more variables take in a sample. Each entry in the table contains the frequency or count of the occurrences of values within a particular group or interval, and in this way, the table summarizes the distribution of values in the sample.

  3. Contingency table - Wikipedia

    en.wikipedia.org/wiki/Contingency_table

    Contingency table. In statistics, a contingency table (also known as a cross tabulation or crosstab) is a type of table in a matrix format that displays the multivariate frequency distribution of the variables. They are heavily used in survey research, business intelligence, engineering, and scientific research.

  4. Letter frequency - Wikipedia

    en.wikipedia.org/wiki/Letter_frequency

    Letter frequency is the number of times letters of the alphabet appear on average in written language. Letter frequency analysis dates back to the Arab mathematician Al-Kindi (c. 801 –873 AD), who formally developed the method to break ciphers. Letter frequency analysis gained importance in Europe with the development of movable type in 1450 ...

  5. Univariate (statistics) - Wikipedia

    en.wikipedia.org/wiki/Univariate_(statistics)

    Univariate is a term commonly used in statistics to describe a type of data which consists of observations on only a single characteristic or attribute. A simple example of univariate data would be the salaries of workers in industry. [1] Like all the other data, univariate data can be visualized using graphs, images or other analysis tools ...

  6. Infrared spectroscopy correlation table - Wikipedia

    en.wikipedia.org/wiki/Infrared_spectroscopy...

    An infrared spectroscopy correlation table (or table of infrared absorption frequencies) is a list of absorption peaks and frequencies, typically reported in wavenumber, for common types of molecular bonds and functional groups. [1][2] In physical and analytical chemistry, infrared spectroscopy (IR spectroscopy) is a technique used to identify ...

  7. Radio spectrum - Wikipedia

    en.wikipedia.org/wiki/Radio_spectrum

    The radio spectrum is the part of the electromagnetic spectrum with frequencies from 3 Hz to 3,000 GHz (3 THz). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particularly in telecommunication. To prevent interference between different users, the generation and transmission of radio ...

  8. Frequency allocation - Wikipedia

    en.wikipedia.org/wiki/Frequency_allocation

    Frequency allocation (or spectrum allocation) is the part of spectrum management dealing with the designation and regulation of the electromagnetic spectrum into frequency bands, normally done by governments in most countries. [1] Because radio propagation does not stop at national boundaries, governments have sought to harmonise the allocation ...

  9. Piano key frequencies - Wikipedia

    en.wikipedia.org/wiki/Piano_key_frequencies

    Piano key frequencies. This is a list of the fundamental frequencies in hertz (cycles per second) of the keys of a modern 88-key standard or 108-key extended piano in twelve-tone equal temperament, with the 49th key, the fifth A (called A 4), tuned to 440 Hz (referred to as A440). [1][2] Every octave is made of twelve steps called semitones.