AP Psychology - Scientific Method, Experimentation, and Research

hypothesis

a testable and falsifiable prediction of a theory

theory

an explanation using an integrated set of principles that organizes observations and predicts behaviors or events (explains phenomenon)

operational definition

a carefully worded statement that specifies how a concept, variable, or term will be measured or observed in a particular study or context

replication

repetition of a research study, usually with different participants in different situations, to determine whether a basic finding can be reproduced

case study

a non-experimental technique in which one individual or group is studied in depth in the hope of revealing universal principles that can generalize a population

naturalistic observation

a non-experimental technique of observing and recording behavior in naturally occurring situations without manipulation or intervention

survey

a non-experimental technique for obtaining the self-reported attitudes or behaviors of a particular group, usually by questioning a random sample

social desirability bias

bias from people reasoning in ways they assume a researcher expects or desires

self-report bias

bias when people report their behavior inaccurately or cannot remember their behaviors

sampling bias

a flawed sampling process that produces a sample that is unrepresentative of a population

random sample

a sample that fairly represents a population because each member has an equal chance of inclusion

population

an entire group of individuals a researcher wants to study or make generalizations about

correlation coefficient

a measure of the extent to which two factors vary together, and thus of how well either predicts the other (from -1.00 to 1.00)

correlation

a statistical index of the relationship between two things

single-blind procedure

an experimental procedure in which the research participants are blind about whether they have received a treatment or a placebo

double-blind procedure

an experimental procedure in which both the research participants and staff are blind about whether the participants received a treatment or a placebo

placebo effect

a phenomenon when a person experiences improvement in a condition after receiving what is believed to be a treatment when in reality the treatment is not chemically active

confounding variable

in an experiment, a factor other than the factor being studied that might influence a study’s results

experimenter bias

bias caused when researchers may unintentionally influence results to confirm their own beliefs

validity

the extent to which a test or experiment measures or predicts what it is supposed to

scientific method

a systematic process of gathering and organizing information through observation and experimentation to answer questions and test ideas objectively

peer reviewers

scientific experts who evaluate a research article’s theory, originality, and accuracy

falsifiability

the possibility that an idea, hypothesis, or theory can be disproven by observation or experimentation

illusory correlation

perceiving a relationship where none exists or perceiving a stronger-than-actual relationship

regression toward the mean

the tendency for extreme or unusual scores or events to eventually fall back (regress) toward the average

quantitative research

an approach using numerical data and statistical analysis to measure and test theories

qualitative research

an approach using words and observations to study human experiences and social realities

informed consent

giving potential participants enough information about a study to enable them to chose whether they wish to participate or not

debriefing

the post-experimental explanation of a study, including its purpose and any deceptions, to its participants

mode

the most frequent occurring value in a data set

mean

the average of a data set; found by adding all the values together and dividing by the number of values

median

the central tendency that represents the middle value in a data set

standard deviation

the statistical measure of how spread out values are from the mean

normal curve

a symmetrical bell-shaped graph that represents data clustered around the mean and taper off to extremes on the ends (34, 13.6, 2.15)

meta-analysis

a statistical procedure for summarizing the results of multiple studies to reach an overall conclusion

statistical significance

a statistical statement of how likely it is that a result occurred by chance, a result is considered statistically significant if the p-value (probability that your results happened randomly by chance) is less than 5% (or 0.05)

descriptive statistics

numerical data used to measure and describe characteristics of groups; like measures of both tendency and variation

inferential statistics

numerical data that allow for one to infer, from sample data, the probability of something being true in a population

percentile rank

the percentage of scores that are lower than a given score

skewed

a representation of scores that lack symmetry around their average score (do not follow the normal curve)

null hypothesis

the preconceived notion that there is no difference in data (the default assumption experimenters test to falsify)