Kin 200 Terminology

Biased sample

A biased sample is drawn in such a way that some members of the population are more likely to be chosen than others.

Experiment/Clinical Trial

A carefully designed study that seeks to determine, under controlled conditions, the effectiveness of a treatment method.

Hawthorne effect

A change in a subject's behavior caused simply by the awareness of being studied

Control variable

A control variable is held constant, or controlled, at one level throughout an experiment. For example, caloric intake would be controlled in a diet study; gender would be controlled in a strength study.

convenience sample

A convenience sample is drawn from an "intact class" or by asking people to volunteer. The sample is not randomly chosen and is typically used because of the ready availability of the subjects. This is a biased sample.

Prospective study (cohort/longitudinal study)

A group of healthy subjects is enrolled and followed over time to determine the frequency with which a specific outcome develops. The sample may be grouped according to the presence or absence of a stimulus variable such as smoking history. Example: A group of smokers and a group of non-smokers were observed across time with the intent of comparing the incidence of lung disease.

ratio level of measurement

A measurement of a variable in which the numbers indicating a variable's values represent fixed measuring units and an absolute zero point

Continuous variable

A quantitative variable that can be reduced to an infinite number of possible values, depending on the accuracy of the measuring instrument. Examples include height, weight, and distance.

random sample

A random sample is drawn in such a way that all members of the population have an equal chance of being selected. This type of sampling is only occasionally used in research with human subjects.

representative sample

A representative sample reflects the characteristics of interest from the target population.

stratified sample

A sample chosen from a population that has been subdivided based upon predetermined characteristics such as gender, race, and socio-economic status. This is the sampling method used for many nationwide polls.

systematic sample

A sample obtained using a pre-determined system (not random); for example, choosing every 10th subject from the population.

Sample

A subset of a population

Parameter

A value, or quantity, that represents a characteristic of a population such as the population mean or standard deviation.

Statistic

A value, or quantity, that represents a characteristic of a sample such as the sample mean or standard deviation.

Independent variable

A variable that you identify as having a potential influence on your outcome measure. This might be a variable that you control, like a treatment. It also might represent a demographic factor like age or gender.

Quantitative variable

A variable whose levels are described numerically. Examples include temperature, % body fat, and time.

Qualitative variable

A variable whose levels are described with words or phrases. Examples include color (red, white, blue), gender (female, male), and size (small, medium, large).

Discrete variable

A variable, either qualitative or quantitative, with a finite number of levels that cannot be subdivided meaningfully. Examples include heart rate, IQ, and color.

Population

All members of a specified group.

double blind study

An experiment in which neither the participant nor the researcher knows whether the participant has received the treatment or the placebo

Rationalistic method

An unscientific method of problem solving in which we derive knowledge through reasoning.

Retrospective study (case control/cross sectional study)

Data is examined from selected cases and controls to determine differences, if any, in the exposure to a suspected factor. Subjects are not "treated," variables are not controlled, and cause & effect may not be inferred. Example: Incidences of premature births were counted among mothers who smoked (case group) and mothers who didn't smoke (control group).

Descriptive statistics

Descriptive statistics are used to describe the basic characteristics of the data in a study. They provide simple summaries about the sample being measured. They can be expressed in numerical and/or graphical form. They form the basis of virtually every quantitative analysis of data

Unsystematic variability

Error, or variability in a measurement, that is caused by something we cannot account for.

extraneous variable

Extraneous Variables are undesirable variables that influence the relationship between the variables that an experimenter is examining. These variables are undesirable because they add error to an experiment. A major goal in research design is to decrease or control the influence of extraneous variables as much as possible.

Establishing cause and effect

Four criteria: (1) The cause and effect must occur close together in time. (2) The cause must happen before the effect. (3) The effect should not happen without the presence of the cause. (4) No plausible alternate explanations exist.

Inferential statistics

Inferential statistics are used to draw conclusions about a population based on information contained in a sample. Information is obtained from a sample and generalized to a population. In this category of statistics, conclusions are made with incomplete information.

Variable

Something that can take on more than one value. A variable might be expected to vary over time. Values of a variable would probably be expected to differ between individuals.

Statistics

Statistics is a mathematical science pertaining to the collection, analysis, interpretation or explanation, and presentation of data. It is applicable to a wide variety of academic disciplines, from the physical and social sciences to the humanities. Statistics are also used for making informed decisions.

Validity

The degree to which an instrument measures what it intends to measure.

internal validity

The degree to which changing the level of the independent variable causes a change in the dependent variable. In an experiment, the highest degree of internal validity exists when all changes in the dependent variable can be attributed to the effect of the independent variable.

external validity

The degree to which the experimental results can be generalized to the target population. The highest degree of external validity exists when all responses from subjects in the sample can be seen in the population. For example, an average loss of 10 pounds in the sample would be mirrored by an average loss of 10 pounds in the population.

measurement error

The failure of identically treated subjects to elicit the same response.

Dependent variable

The outcome measure; the variable that is measured in a research study. It is affected by, or "dependent" on, the actions of other variables such as the independent variable(s).

"Levels" of a variable

The various values that a variable may assume. For example, red, white, and blue are among the levels of the variable "color." Levels of the variable "G.P.A." include: 2.5, 3.2, and 4.0.

systematic variability

Variability in a measurement that is caused by something we can account for.

Nominal Level of measurement

Variables are categorical, qualitative, and discrete in nature. Although numbers can be used to represent levels of the variables, the numbers are treated as labels. Examples include brand of shoes, Social Security number, and gender.

Oridinal level of measurement

applies to data that can be arranged in order. However, differences between data values either cannot be determined or are meaningless.

placebo effect

experimental results caused by expectations alone; any effect on behavior caused by the administration of an inert substance or condition, which the recipient assumes is an active agent.

avis effect

participants in control group try harder because they are in control group

interval level of measurement

ranks data, and precise differences between units of measure do exist; however, there is no meaningful zero

Reliability

repeatability of a measurement

single-blind study

study in which the subjects do not know if they are in the experimental or the control group

random assignment

subjects are randomly assigned to treatment and control groups. This is not random sampling - it occurs after the sample has been chosen.

Rosenthal effect

the result when an experimenter's preconceived idea of appropriate responding influences the treatment of participants and their behavior