Two group design

chapter 8

double-blind assignment

ensures that research participants do not know which conditions they are in and this controls for a possible placebo effect. Researcher is also blind to treatment each participant is receiving -- reduces possible experimenter bias.

independent variable

the variable being manipulated in the experiment (in order to study its effect). the variable that influences the dependent variable.

dependent variable

the variable being measured in an experiment (to test outcome of manipulation of IV). the variable measured in association with changes in the independent variable; the outcome or effect.

internal validity

the degree to which we can rule out other possible causal explanations for an observed relationship between the independent and dependent variables

temporal precedence

when changes in the suspected cause (treatment) occur before changes in the effect (outcome)

experimental group

the group or condition that gets the key treatment in an experiment

covariation

when changes in one variable are associated with changes in another variable; part of determining causality

control group

any condition that serves as the comparison group in an experiment

mundane realism

the degree to which a study parallels everyday situations in the real world

two-group design or simple experiment

an experimental design that compares two groups or conditions and is the most basic way to establish cause and effect; also known as a simple experiment

experimental control

the ability to keep everything between groups the same except for the one element we want to test in an experiment.

extraneous variable

a factor other than the intended treatment that might change the outcome variable

experimental hypothesis

a clear and specific prediction of how the independent variable will influence the dependent variable

experimental realism

the degree to which a study participant becomes engrossed in the manipulation and truly influenced by it

matched-pair design

a design in which one creates a set of two participants who are highly similar on a key trait and then randomly assigns individuals in the pair to different groups

independence

the assumption that each participant represents a unique and individual data point

random assignment

any method of placing participants in groups that is nonsystematic and nonbiased, and that ensures each participant has an equal chance of being in any group

manipulation check

a measure that helps determine whether the manipulation effectively changed or vaired the independent variable across conditions

researcher notes

a place to keep track of anything out of the ordinary that happens during the study

effect size

a statistical measure of the magnitude of the difference between groups

null hypothesis

the hypothesis of no difference; usually the hypothesis the researcher is trying to statistically reject

t-test for independent means

a statistical test comparing groups' means to see if the groups differ to a degree that could not have happened accidentally or by chance; also known as an independent samples t-test

Nonexperimental design

a design in which there is no control or manipulation of the independent variable; cause-and-effect relationships between variables cannot be established

experimental design

a research method in which the experimenter controls and manipulates the independent variable, allowing the establishment of cause-and-effect relationships between the independent and dependent variables

behavioral choice

a behavioral measure involving participants making a purposeful selection from several options

behavioral trace

a behavioral measure that relies on evidence left behind by participants who are no longer present

behavioral observation

a behavioral measure that relies on directly seeing or observing behavior

the t score represents..

the size of the difference between the groups relative to the amount of overall difference in the sample

the significance level or p level represents…

the probability that the results happened by chance. The lower the p level, the less likely the results happened by chance.

The t score and p level will only tell you whether there is a ___ __difference. To determine the nature or direction of that difference, you need to look at the__ ____

significant, means

correlation coefficient

a measure of both the direction and strength of a correlation. represented by the letter r.

the closer r gets to 1, the ____ the relationship is between the variables

stronger

what strength is the r value 0?

zero or none

what strength is r = 0.1-0.3

weak

what strength is 0.4-0.6 r?

moderate

what strength is 0.7-0.9 r?

strong

what strength is 1 r?

perfect

a negative correlation (-r) means that

as one variable increases, the other decreases

a positive correlation means (+r)

as one variable increases, so does the other

the closer r gets to 0, the ____ the relationship

weaker

the closer the p value gets to the alpha (0.05) the less likely the results are significant. this means they are more or less likely to be due to chance?

more likely to be due to chance