The research glossary defines terms used in conducting social science and policy research, for example those describing methods, measurements, statistical procedures, and other aspects of research; the child care glossary defines terms used to describe aspects of child care and early education practice and policy.
Basic statistics used to describe and summarize data. Descriptive statistics generally include measures of the average values of variables (mean, median, and mode) and measures of the dispersion of variables (variance, standard deviation, or range).
Variables that have only two categories, such as whether a child is enrolled in a preschool program or not.
Differential or selective attrition occurs when the rates of dropping out or leaving a study with several data collection waves (e.g., longitudinal study or experimental research) vary across different study groups. This is particularly troublesome when the characteristics of those who drop out are systematically different from those who remain, and may introduce bias in the study findings.
The effect of one variable on another variable, without any intervening variables.
A method of gathering data primarily through close visual inspection of a natural setting. Direct observation does not involve actively engaging members of a setting in conversations or interviews. Rather, the direct observer strives to be unobtrusive and detached from the setting.
A procedure whereby, during an open-ended interview,\ a researcher actively seeks accounts from other respondents that differs from the main or consensus accounts in critical ways
A variable that can assume only a finite number of values; it consists of separate, indivisible categories. The opposite of discrete is continuous. For example, in a specified time period, a child's biological parents either live in the same household as the child or they do not. In contrast, a child's height could be 3 feet 1 inch, 3 feet 1.1 inches, 3 feet 1.11 inches, and so on, thus it is continuous variable.
A grouping method that identifies characteristics that distinguish between groups. For example, a researcher could use discriminant analysis to determine which characteristics identify families that seek child care subsidies and which identify families that do not.
In statistics, dispersion refers to the spread of a variable's values. Techniques that are used to describe dispersion include range, variance, standard deviation, and skew.
The frequency with which values of a variable occur in a sample or a population. To graph a distribution, first the values of the variables are listed across the bottom of the graph. The number of times the value occurs are listed up the side of the graph. A bar is drawn that corresponds to how many times each value occurred in the data. For example, a graph of the distribution of women's heights from a random sample of the population would be shaped like a bell. Most women's height are around 5'4" This value would occur most frequently, so it would have the highest bar. Heights that are close to 5'4", such as 5'3" and 5'5" would have slightly shorter bars. More extreme heights, such as 4'7" and 6'1" would have very short bars.