Chap 6

• Independent variable


  The manipulated variable (cause)
• Dependent variable


  The variable that is measured (effect)
• Control variable


  variable that is constant in both groups
• Experimental group


  The group receiving or reacting to the independent variable
• Control group


  group that doesn't receive the independent variable but should be kept identical in all other aspects
• Population


  group of interest
• Representative sample


  sample that reflects the diverse characteristics of the population that is being studied. either random or not random
• Random sampling


  Randomly chosen subjects are randomly assigned into both the experimental and control groups. To ensure that each group has minimal differences
• Why was there sampling bias in the survey during the 1948 US Election between Harry Truman and Thomas Dewey

  Because not everyone had phones, so the survey undercounted young voters
• Bias of selection (from a specific real area)


  occurs when people are selected in a physical space
• Self-selection bias


  When people being studied have some control over whether or not to participate
• Pre-screening or advertising bias


  how volunteers are screened or where advertising is placed might skew the sample
• Healthy user bias


  Occurs when the study population tends to be in better shape than the general population
• Single-blind design


  subjects do not know whether they are in the control or experimental group
• Double-blind design


  neither the subjects nor the researcher knows who is in the two groups. Designed so that the experimenter does not inadvertently change the responses of the subjects (eg. change of voice)
• In some double-blind experiments, the control group is given..

  a placebo
• Correlational research


  Researchers do not directly manipulate variables, but rather observe naturally occurring differences.
• Confounding variable


  Third variable or extraneous variable. The unknown factor playing a role in correlational research
• A commonly used correlational research method

  surveys
• Social desirability bias / courtesy bias


  when people respond with what they think is socially desirable, or what the questioner wants to hear
• Clinical studies often take the form of

  Case studies
• Case studies


  intensive psychological studies of single individuals under the assumption that an in-depth understanding of single cases will allow for general conclusions about other similar cases.
• When conducting case studies, researchers try to ensure that their studies are

  generalizable, or applicable to similar circumstances because of the predictable outcomes of repeated tests
• Conceptual definition


  the theory or issue being studied
• Operational definition


  the way in which that theory or issue will be directly observed or measured in the study
• Internal Validity


  the certainty with which the results of an experiment can be attributed to the manipulation of the independent variable rather than to some other confounding variable
• External Validity


  extent to which the findings of a study can be generalized to other contexts in the "real world"
• Principal threat to internal validity

  confounding variables (variables that haven't been adequately controlled by the experimenter)
• Principal threat to external validity

  the often artificial nature of the experimental environment
• reliability of an experiment

  whether or not the same results appear if the experiment is repeated under similar conditions
• inter-rater reliability


  degree to which different raters agree on their observations of the same data
• advantage of naturalistic observation


  allows the study of authentic real-world behaviors
• disadvantage of naturalistic observation

  difficulty of controlling for the numerous extraneous variables present in real-world environments, which can limit the reliability of findings
• Descriptive statistics


  summarize data
• inferential statistics


  allow researchers to test hypotheses about data and determine how confident they can be in their inferences about the data
• Commonly used descriptive statistics

  Mean, mode, median
• What do mean mode median measure

  central tendency
• If there are two modes, then the set of data is

  bimodal
• Mean mode and median can be represented in a

  normal curve
• In a perfectly normal distribution,

  the mean, mode, median are all identical