Senior Research Exam 2

• overview of experimental research


  traditional type of research; purpose is to investigate cause and effect relationships among variables; experimental vs control groups; each group of participants receives a different treatment; always involves manipulation of the IV
• 3 criteria for cause and effect

  the cause must precede the effect; the cause and effect must be correlated with each other; the correlation between cause and effect cannot be explained by another variable; if the condition is necessary and sufficient to produce the effect, then it is the cause
• internal validity


  did the treatments (IV) cause the change in the outcome (DV)
• external validity


  to what populations, setting, or treatments can the outcome be generalized
• internal/external validity trade-off


  increase internal validity at the expense of external
• threats to internal validity


  history, maturation, testing, instrumentation, statistical regression, selection biases, experimental mortality, selection-maturation interaction, expectancy
• history


  event that are not part of treatment
• maturation


  events due to passage of time
• testing


  effects of more than one test administration (experience, etc)
• instrumentation

  change in calibration of measurements
• statistical regression


  selection based on extreme score
• selection bias

  nonrandom participant selection
• experimental mortality


  differential loss of participants
• selection-maturation interaction


  passage of time influencing groups differently
• expectancy


  influence of experimenters on participants (when people know they're in a study they may act differently)
• ways to control threats to internal validity

  randomization, placebos, blind setups, double-blind setups, reactive effects of testing: eliminate pretest, instrumentation, experimental mortality: increase numbers
• randomization

  real randomization; matched pairs (not groups); randomizing treatments or counterbalancing
• threats to external validity

  reactive or interactive effects of testing; interaction of selection biases and treatment; reactive effects of experimental arrangements; multiple-treatment interference
• reactive or interactive effects of testing


  pretest may make participants sensitive to treatment
• interaction of selection biases and treatment

  treatment may work only on participants selected on specific characteristics
• reactive effects of experimental arrangements

  setting constraints may influence generalizability
• multiple-treatment interference


  one treatment may influence the next treatment (ex: different types of stretching= cumulative effect)
• ways to control threats to external validity

  selecting from a larger population for participants, treatments, situations; ecological validity
• ecological validity

  does the setting capture the essence of the real world; people react differently in different settings
• pre-experimental design


  weak experimental designs in terms of control; no random sampling; threats to internal and external validity are significant problems; many definite weaknesses; ex: one-group pretest/posttest design
• true experimental design


  best type of research design because of their ability to control threats to internal validity; utilizes random selection of participants and random assignment to groups; ex: pretest/posttest control group design
• quasi-experimental design


  lack either random selection of participants or random assignment to groups; lack some of the control of true exp designs, but are generally considered to be fine; ex: nonequivalent group design
• methods of control


  physical manipulation; selective manipulation= matched pairs and counterbalanced; statistical techniques
• matched pairs design


  participants matched according to some key variable then randomly assigned to treatment group (ex: male/female to make sure same # in each group)
• block design


  extension of matched pairs to 3 or more groups; ex: grade in school
• counterbalanced design


  all participants receive all treatments but in different orders; to avoid fatigue effect and practice effect
• common sources of error

  many possible sources of error can cause the results of a research study to be incorrectly interpreted; threats to the validity of a study
• sources of error examples

  hawthorne effect; placebo effect; rating effect; experimenter bias effect
• hawthorne effect


  specific type of reactive effect in which merely being a research participant in an investigation may affect behavior
• placebo effect


  participants may believe the experimental treatment is supposed to change them
• rating effect


  Halo; overrator; underrator; central tendency= people tend to be in the middle (not extremes)
• experimenter bias effect


  single vs double blind
• halo effect

  people rating tend to stick to the same numbers
• descriptive research


  experimental research focuses on future; descriptive research is focused towards the present= gathering info and describing the current situation; may or may not involve hypothesis testing; are not manipulating a variable
• questionnaires


  determining objectives; delimiting the sample (describing)= most common; constructing the questionnaire