 | Term | Definition |
| |
sample |
subgroup of the population that participates in the study |
| |
random selection |
choosing of members of a population so that every individual has an equal chance of being chosen |
| |
experimental group |
the subgroup of the sample that receives the treatment or independent variable |
| |
control group |
the comparison group; the subgroup of the sample that is like the experimental group in every way except for the presence of the independent variable |
| |
random assignment |
division of the sample into groups so that every individual has an equal chance of being put in any group or condition |
| |
confounding variables |
differences between the experimental group and the control group other than the independent variable |
| |
operational definition |
a description of the specific procedure used to determine the presence of a variable |
| |
experimenter bias |
a phenomenon that occurs when a researcher's expectations or preferences about the outcome of a study influence the results obtained |
| |
demand characteristics |
clues participants discover about the purpose of the study that suggest how they should respond |
| |
single-blind procedure |
research design in which partiicpants don't know whether they are in the experimental or control group |
| |
double=blind procedure |
research design in wheihc neither the experimenter nor the participants know who is in the experimental group and who is in the control group |
| |
placebo |
a physical or psychological treatment given to the control group that resembles the treatment given to the experimental group, but contrains so active ingredient |
| |
placebo effect |
a response to the belief that the independent variable will have an effect, rather than the actual effect of the independent variable, which can be a confounding variable |
| |
reliability |
consistency or repeatability of results |
| |
validity |
the extent to which an instrument measures or predicts what it is supposed to measure or predict |
| |
statistics |
a field that involves the analysis of numerical data aobut representative samples of populations |
| |
descriptive statistics |
numbers that summarize a set of research data obtained from a sample |
| |
frequency distribution |
an orderly arrangement of scores indicating the frequency of each score or gorup of scores |
| |
central tendency |
aveage or most typical scores of a set of research data or distribution |
| |
mode |
most frequently occurring score in a set of research data |
| |
median |
the middle score when a set of data is ordered by size |
| |
mean |
the arithmetic average of a set of scores |
| |
variability |
the spread or dispersion of a set of research data or distribution |
| |
range |
the difference between the largest score and the smallest score |
| |
standard deviation (SD) |
measures the average difference between each score and the mean of the data set |
| |
normal distribution |
bell-shaped curve that represents data about how lots of human characteristics are dispersed in the population |
| |
percentile score |
the percentage of scores at or below a particular scores |
| |
correlation coefficient (r) |
a statistical measure of the degree of relatedness or association between two sets of data that ranges from -1 to +1 |
| |
inferential statistics |
statistics that are used to interpret data and draw conclusions |
| |
statistical significance (p) |
the condition that exists whenthe probability that observed findings are due to change is less than 1 in 20 (p less than .05) |
| |
ethical guidelines |
suggested rules for acting responsibily when conducting research or in clinical practice |
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