Educational psychology : an objective study / by Peter Sandiford.

  • Sandiford, Peter, 1882-1941.
Date:
1928
Catalogue details

Licence: In copyright

Credit: Educational psychology : an objective study / by Peter Sandiford. Source: Wellcome Collection.

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    the answers. It is in this regard that intelligence tests, by the mechanics of their construction, have achieved their best results. The instructions for scoring are so precise and the arrangements of the items so excellent, that few tests to-day, if marked by different examiners, yield different scores. The terms ease of administration and scoring explain them¬ selves. Intelligence tests usually rank highly in both these features The satisfactoriness of the norms depends upon their form and accuracy. The norm, as we have seen, may be a mean, a median, a measure of variability, a percentile, etc., calculated for any special group. If a central tendency is used, the probable error, calculated from the standard formula, provides a good index of accuracy. But, as we remarked in the section dealing with standardization, all norms must be secured from a fair sampling of the population under consideration. The Distribution of Intelligence.—Since intelligence is a native trait we should expect it to be distributed, like all other natural variants, according to the curve of chance. There is a vast accumulation of evidence to show that this is the form of distribution actually followed. Terman 1 reported the distribu¬ tion of I.Q.’s of 1,000 unselected American children to be the following : IQ. Percentage falling 56-65 o-33 66-75 23 76-85 8-6 86-95 20-1 96-105 33*9 106-115 231 116-125 90 126-135 2*3 136-145 0-55 Total . • 10018 The distribution closely follows the curve of chance. The various grades of intelligence are symmetrically grouped about the central tendency and decrease gradually without abrupt changes towards the two extremes. Any division of intelligence into groups such as genius, normal, feeble-minded, etc., is an arbitrary proceeding since no sharp lines of demarcation can be drawn at any point. Nevertheless the divisions drawn in Table X have been found useful in practice, although they have undoubtedly encouraged the belief among the unthinking that they represented a sharply defined and immutable classification. 1 Terman, Measurement of Intelligence, p. 66.