International Commission on Irrigation & Drainage Commission Interationale des Irrigation et du Drainage

Multilingual Technical Dictionary (MTD)
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Term No.Term Name/Term DescriptionAction
6
Accuracy of the mean
The closeness of agreement between the true value and the mean result obtained by applying the experimental procedure to a very large number of times. The smaller the systematic part of the experimental errors which affect the results, the more accurate is the procedure......
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11
Chi-squared statistic
A statistic distributed as chi-squared (c²), namely the sum of squares of independent standard normal variables, widely used to test agreement between observation and hypothesis......
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105
Arithematic mean
The arithmetic mean of a set of values. Generally denoted by a bar, thus :
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107
Consecutive average, Moving average, or Consecutive mean
The mean of a small group of consecutive values, especially annual means, assigned to the middle time-term of the group in the process of smoothing, e.g. 5-year mean......
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109
Geometric mean
If the set of n values are all multiplied together and the nth root is taken, the results are known as the geometric mean (G), viz. G = (x1 . x2 ... x n-1 . xn)1/n .....
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110
Harmonic mean
The reciprocal of the arithmetic mean of the reciprocals of each observation.
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113
Weighted average, or Weighted mean
An average of quantities that attaches a series of weights to it in order to make proper allowance for their relative importance. A value obtained by multiplying each of a series of values by its assigned weight and dividing the sum of those products by the sum of the weights. For example, a weighted arithmetic mean of x1, x2 ... xn with weights w1.....
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114
Root mean square
The square root of the arithmetic mean of the squares of each observation and is given by
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117
Average deviation, or Mean deviation
A measure of dispersion derived from the average deviation of observations from some central value, such deviations being absolute, i.e. without reference to algebric sign......
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129
Mean square
In general, the mean square of a set of values is the arithmetic mean of the squares of their differences from some given value, namely their second moment about that value......
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134
Standardized averages, or Standardized means
A method of allowing or `adjusting` the effects of other variables, or for differences in the composition of the groups that are to be compared, by using a standard set of weights to combine the means of sub-groups into a single mean. Used mainly for the construction of index numbers......
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148
Chi-squared distribution
If x1, x2, ... xv are a sample of v independent normally distributed random variables, each with zero mean and unit variance, the random variable x² = x1² + x2² + ------ + xv² gives the chi-square distribution with v degrees of freedom......
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190
Chi-squared test
The test of significance based upon the chi-squared statistic c2.
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208
Mean square error of estimate
The square root of the arithmetic mean of the squared deviations between the estimates for different samples and the population parameter under estimation......
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243
Least square method
A method of determining the arbitrary constants in the equation of a curve, based upon the principle that the most probable value of a quantity to be deduced from a set of measurements is obtained by making the sum of the squares of the residual (deviations from it) a minimum......
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244
Least square line
A relationship between variates obtained by minimizing the mean-squared vertical deviations from the `regression line` where the regression between the variates is linear......
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269
Least square fit
A straight or curvilinear trend to give the mean of the squared vertical deviations as minimum. See 244.
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278
Mean consecutive
The mean of a small group of consecutive values, especially annual means, assigned to the middle time-term of the group, in the process of `smoothing`......
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472
144 square inches
img:equations//472_476_e.jpg
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473
9 square feet
img:equations//472_476_e.jpg
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474
1210 square yards
img:equations//472_476_e.jpg
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624
Kilograms-force per cm square
img:equations//596_630_e.jpg
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759
Mean annual precipitation
The average over a period of years of the annual amounts of precipitation.
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760
Weighted mean monthly precipitation
The weighted mean precipitation for each month for a large area derived from the study of the isohyetal map of the area.
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847
Mean annual runoff
The value of the annual volume of water discharged by the stream drainage of the areausing  sufficiently long record to obtain a fair mean......
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