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z test
parametric inferential statistical test of the null hypothesis for a single sample wehre the population variance is known.
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sampling distribution
distribution of sample means based on random samples of a fixed size from a population.
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standard error of the mean
standard deviation of the sampling distribution
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central limit theorem
states that ofr any population with a mean µ and a standard deviation σ, the distribution of sample means for sample size N will have a mean of µ, a standard deviation of σ/√N, and will approach a normal distribution as N approaches infinity.
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critical value
value of a test statistic that marks the edge of the region of rejection in a sampling distribution, where values equal to it or beyond it fall in the region of rejection.
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region of rejection
are of a sampling distribution that lies beyond the test statistic's critical value; when a score falls within this region, H0 is rejected.
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statistical power
probability of correctly rejecting a false H0.
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confidence interval
an interval of a certain width that we feel confident will contain µ.
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t test
a parametric inferential statistical test of the null hypothesis for a single sample where the population variance is not known.
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student's t distribution
a set of distributions that, although symmetrical and bell-shaped, are not normally distributed.
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degrees of freedom (df)
the number of scores in a sample that are free to vary.
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estimated standard error of the mean
an estimate of the standard deviation of the sampling distribution.
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chi-square (x2) goodness-of-fit test
nonparametric inferential procedure that determines how well an observed frequency distribution fits an expected distribution.
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observed frequency
the frequency with which participants fall into a category.
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expected frequency
the frequency expected in a category if the sample data represent the population.
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a __ is a distribution of sample means based on rndom samples of a fixed size from a population
sampling distribution
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the __ is the standard deviation of the sampling distribution.
standard error of the mean
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the set of distributions that, although symmetrical and bell-shaped, are not normally distributed is called the ___.
student's t distribution
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the ___ is a parametric statistical test of the null hypothesis for a single sample where the population variance is not known.
t test
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___ and ___ frequencies are used in the calculation of the x2 statistic.
observed; expected
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inferential statistics allow us to infer something about the __ based on the ___.
population; sample
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the sampling distribution is a distribution of:
sample means
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a one-tailed z test is to ____ and a two-tailed z test is to ___.
±1.645; ±1.96
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which of the following is an assumption of the t test?
the sample size is typically less than 30.
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parametric is to nonparametric as ____ is to ____.
t test; x2 test
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which of the following is an assumption of x2 tests?
the sample should be randomly selected.
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between-subjects design
an experiment in which different subjects are assigned to each group.
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posttest-only control group design
an experimental design in which the dependent variable is measured after the manipulation of the independent variable.
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pretest/posttest control group design
an experimental design in which the dependent variable is measured both before and after manipulation of the independent variable.
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confound
an uncontrolled extraneous variable or flaw in an experiment.
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internal validity
the extent to which the results of an experiment can be attributed to the manipulation of the indpendent variable rather than to some confounding variable.
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history effect
a threat to internal validity in whch an outside event that is not a part of the manipulation of the experiment could be responsible for the results.
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maturation effect
a threat to internal validity in which naturally ourring changes within the subjects could be responsible for the observed results.
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testing effect
threat to internal validity in which repeated testing leads to better or worse scores.
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regression to the mean
a threat to internal validity in which extreme scores, upon retesting, tend to be less extreme, moving toward the mean.
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instrumentation effect
a threat to internal validity in which changes in the dependent variable may be due to changes in the measuring device.
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mortality (attrition)
threat to internal validity in which differential dropout rates may be observed in the experimental and control groups, leading to inequality between the groups.
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diffusion of treatment
When a treatment given in a study group is shared with members of a control group.
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experimenter effects
- the results of the study are biased by the experimenter's expectations.
- influence of the experimenter's behavior, personality traits, or expectancies on the results of his or her own research.
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single-blind experiment
experimental procedure in which either the subjects or the experimenters are blind to the manipulation being made.
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double-blind experiment
experimental procedure in which neither the experimenter nor the subject knows the condition to which each subject has been assigned; both parties are blind to the manipulation.
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subject effect
changes in the behaviors or responses of the participants may be due to information received from others participating in the experiment.
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placebo group
group of subjects who believe they are receiving treatment but in reality are not.
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placebo
simulated or otherwise medically ineffectual treatment for a disease or other medical condition intended to deceive the recipient.
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floor effect
limitation of the measuring instrument that decreases its capability todifferentiate between scores at the bottom of the scale.
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ceiling effect
limitation of the measuring instrument that decreases its capability todifferentiate between scores at the top of the scale.
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external validity
the extent to which the results of an experiment can be generalized.
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college sophomore problem
an external validity problem that results from using mainy college sophomores as subjects in research studies.
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exact replication
repeating a study using teh same means of manipulating and measuring the variables as in the original study.
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conceptual replication
study based on another study that uses different methods, a different manipulation, or a different measure.
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systematic replication
study that varies from an original study in one systematic way--for example, by using a different number or type of subjects, a different setting, or more levels of the independent variable.
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correlated-groups design
an experimental design in which the subjects in the experimental and control groups are related in some way.
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within-subjects design
type of correlated-groups design in which the same subjects are used in each condition.
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order effects
problem for within-subjects designs in which the ordre ofthe conditions has an effect on teh dependent variable.
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counterbalancing
mechanism for controlling order effects either by including all orders of treatment presentation or by randomly determining the order for each subject.
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latin square
counterbalancing technique to control for order effects without using all possible orders.
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matched-subjects design
a type of correlated-groups design in which subjects are matched between conditions on variable(s) that the researcher believes is (are) relevant to the study.
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experiment in which different subjects are assigned to each group is a ___.
between-subjects design
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when we use ___, we randomly determine who serves in each group in an experiment.
random assignment
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when the dependent variable is measured both before and after manipulation of the independent variable, we are using a ___ design.
pretest-posttest control group design
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___ is the extent to which the results of an experiment can be attributed to the manipulation of the independent variable, rather than to some confounding variable.
internal validity
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a(n) ___ is a threat to internal validity where the possibility of naturally occurrng changes within the subjects is responsible for the observed results.
maturation effect
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if there is a problem with the measuring device, then there may be a(n) ___ effect.
instrumentation
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if subjects talk to each other about an experiment, then there may be ____.
diffusion of treatment
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when neither the experimenter nor the subjects know the condition to which each subject has been assigned, a ___ experiment is being used.
double-blind
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when the measuring device is limited in such a way that scores at the top of the scale cannot be differentiated, there is a ___ effect.
ceiling
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the extent to which the results of an experiment can be generalized is called ___.
external validity
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when a study is based on another study but uses different methods, a different manipulation, or a different measure, we are conducting a ___ replication.
conceptual
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if the order of conditions affects the results in a within-subjects design, there are ____.
order effects
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manipulate is to measure as __ is to ___.
independent variable; dependent variable
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in an experimental study of the effects of stress on appetite, stress is the:
independent variable
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in an exprimental study of the effects of stress on appetite, subjects are randomly assigned to either the no-stress group or the stress group. these groups represent the __ and the __, respectively.
control group; experimental group
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within-subjects design is to between-subjects design as __ is to ___.
using the same subjects in each group; using different subjects in each group.
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the extent to which the results of an experiment can be attributed to the manipulation of the independent variable, rather than to some confounding variable refers to:
internal validity
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Joann conducted an experiment to test the effectiveness of an anti-anxiety program. the experiment took place over a 1-month time period. subjects in the control group and the experimental group (those who participated in the anti-anxiety program) recorded their anxiety levels several times each day. Joann was unaware that midterm exams also happened to take place during the 1-month time period of ther experiment Joann's experiment is now confounded by:
history effect
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Joe scored very low on the SAT the first time he took it. based on the confound of __, if Joe were to retake the SAT, his score should __.
regression to the mean; increase
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when the confound of mortality occurs:
subjects are lost differentially from the experimental and control groups.
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controlling subject effects is to controlling both subject and experimenter effects as __ is to __.
single-blind experiment; double-blind experiment.
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if you wer to use a bathroom scale to weigh mice in a experimental setting, your experiment would most likely suffer from a:
floor effect.
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if we were to conduct a replication in which weincreased the number of levels of the independent variable, we would be using a(n) ___ replication.
systematic
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most psychology experiments suffer from the __ problem because of the type of subjects used.
college sophomore problem
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