Download PDF STATISTICS IN PSYCHOLOGY AND EDUCATION BY HENRY E. GARRETT

Sinopsis

In the measurement of mental and social traits or capacities most of the facts with which we deal fall into what are known as continuous series. A continuous series may be defined simply as a series which is theoretically capable of any degree of subdivision. JQ's, for example, are generally thought of as increasing by increments of 1 on a scale which extends from the idiot to the genius; however, there is actually no real reason at least theoretically why with more refined methods of measurement we should not be able to get IQ's of 100.8 or even 100.83. Nearly all capacities measured by mental and educational tests and scales, as well as such attributes as height, weight, cephalic index, etc., have been found to be continuous, so that within the range of the scale used, any measure integral or fractional may exist and have meaning. Whenever gaps occur in a truly continuous series, therefore, these are usually to be attributed to our failure to measure enough cases, or to the relative crudity of our measuring instruments, or to some other fact of the same sort, rather than to the fact that no measures exist within the gaps.

There are, however, measures which do not fall into continuous series. Thus a salary scale in a department store may run from $10 per week to $20 per week in units of 50 cents or $1.00; no one receives, let us say, $17.53 per week. Or, to take another example, the average family in a certain locality may work out mathematically to be 4.57 children, although there is obviously a real gap between four and five children. Series like these, which contain real gaps, are called discrete or discontinuous. It is probably fortunate—at least from the standpoint of the beginner in statistics—that nearly all of the measures which we make in psychology are continuous or can be treated as continuous. This considerably simplifies the problem, inasmuch as we may concern ourselves (for the present at least) almost entirely with methods of handling continuous data, postponing the discussion of discrete series to a later page.

Content

1. The Tabulation of Measures into a Frequency Distribution
2. Measures of Central Tendency
3. Measures of Variability
4. The Short Method of Finding the Average, AD, and SD(a)
5. The Comparison of Groups
6. The Calculation of the Percentiles in a Frequency Distribution
7. When to Use the Different Measures of Central Tendency and Variability
8. Summary of Formulas for Finding the Measures of Central Tendency and Variability

Click here to download