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Appendix: Discrete Algebra

The range and interquartile range are measures of dispersion of a set of data. The range is the difference between the largest and smallest numbers. The inter- quartile range is the difference between the upper and lower quartiles.

The mean is another measure of central tendency. It is the sum of the numbers divided by the number of numbers in the set.

Statistics involves the manipulation of these values most of the time. If you want to know more about statistics, you should consult your local library for more information.

# Matrices

Matrices are the actual use of the statistic or the collected data. Each number is put into a row or a column in a matrix. The matrices come in different dimensions. The most commonly used are 2x2, 3x3, and 4x4.

When you add two matrices, you add the corresponding numbers. The first number in the first row in the first matrix adds to the first number in the first row in the second matrix. When you multiply two matrices, you multiply the row to the column. The first number in the first row in the first matrix multiplies to the first number in the first column in the second matrix. The second number in the first row in the first matrix multiplies to the second number in the first column in the second matrix. After you have multiplied every number in the row to the every number in the corresponding column, you add the results together to get the number for the resulting matrix.

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