ch 11 research methods confounding variables

maturation is a threat to internal validity, what does it mean

participants naturally change over time, emerging more or less spontaneously over time

history is a threat to internal validity, what does it mean 

when an event occurs at the same as the treatment and changes participants behavior, difficult to infer treatment has an effect 

regression to the mean is a form of selection bias and a threat to internal validity, what does it mean

individuals sometimes peform very well or very poorly because of chance

attrition/mortality is a threat to internal validity, what does it mean

when participants are lost from the study, group equivalence formed at the start of study may be destroyed

• mortality across groups is okay, but within a group is not

testing threat is a threat to internal validity, what does it mean

kind of order effect in which scores change over time because participants have taken the test more than once, includes practice effects

how can instrumentation/measurement a threat to internal validity 

can change over time, like when observers become bored or tired 

-ex; when protection program is implemented, reporting laws change such as what constitutes as assault is broadened

how can non equivalent groups/selection effects be a threat to internal validity

when differences exist between individuals in treatment and control groups at the start of the study, fixed my random assignment

• can we tell if the new recycling program is effective when comparing weight of garbage from participants in program from those not in program

how can additive effects with selection be a threat to internal validity

when one groups of participants in an experiment respond differently to an external event, matures at a different rate or is measured more sensitively by a test (instrumentation)

what is one group, pretest/posttest design 

one group recruited to be measured on pretest (treatment or intervention) and then measured on a posttest 

what is experimenter/observer bias

occurs when a researcher inadvertently treats groups differently in the study due to knowledge of the hypothesis for the study

what is social desirability

participants present themselves in a more desirable way

what are demand characteristics 

participants try to figure out the study and change behaviors to match expectations 

what is diffusion of treatment

when subjects in one condition share information about the study with subjects in the other condition

what is a double blind study

neither participants nor researchers who evaluate them know who is in the treatment group and who is in the comparison group

what is a masked design 

observers are unaware of the experimental conditions to which participants have been assigned 

what is placebo effects

people recieving an experimental treatment experience a change because they believe they are recieving a valid treatment

what is a double blind placebo control study

uses treatment group and a placebo group and neither researchers or participants know who is in which group

with not comparison group, what must you rule out 

history, maturation, testing, instrumentation, regression, subject attrition, and selection

when there is a comparison group, what must you rule out

selection, differential regression, and additive effects with selection

why is contamination a threat that a true experiment can not eliminate 

communication of information about the experiment between groups

• resentment, rivalry, and diffusion of treatment 

why is experimenter expectancy effects a threat that true experiments may not eliminate

they unintentionally influence results

what is a novelty effect

temporary boost in performance that occurs when a person is exposed to something new or different

what are disruption effects 

negative consequence when something significant alters a persons normal routine 

what is a measurement error

any factor that can inflate or deflate a person true score on the DV

what is power

likelihood that a study will show a statisitcally significant result when an IV truly has an effect on a population

what is a null effect

finding an IV did not make a difference in the dependent variable, there is no covariance 

what is a ceiling effect

IV scores and DV scores both fall at the high end of their possible distribution

what is a floor effect

both IV and DV scores fall at the low end of their possible distribution

what is a manipulation check

extra DV measures included to determine how well a manipulation worked 

what is noise

causes unsystematic variability by individual differences or measurement error

what is situation noise

unrelated events or distractions in the external environment that create unsystematic variability within groups in an experiment