Untitled Flashcards Set

Ch 10 

• Experimental variables 

  • Independent and dependent 

    • Dependent- outcome variable 

      • Researchers have less control over dependent variable 

    • Experiments often have more than one dependent variable 

  • Independent (causal) variable is almost always on the x axis 

  • Dependent variable is almost always on y axis 

  • Control variables- held constant on purpose 

    • Not rly variables 

    • Allow researchers to separate one potential cause from another and thus eliminate alternative explanations for results 

    • Important for establishing validity 

  • Covariance- the results show that the causal variable is related to the outcome variable. Distinct levels of the independent variable are associated with different levels of the dependent variable 

  • Temporal precedence- the study design ensures that the causal variable comes before the outcome variable in time 

  • Internal validity- the study design rules out alternative explanations for the results 

  • Manipulating the independent variable is necessary for establishing covariance, but the results matter too. 

• Design confound- experimenters mistake in designing the independent variable 

  • Occurs when a second variable happens to vary systematically along with the intended independent variable 

  • Threat to internal validity 

• Systematic variability- description of when the levels of a variablw coincide in some predictable way with experimental group membership, creating a potential confound 

• Unsystematic variability- a description of when the levels of a variable fluctuate independently of experimental group membership, contributing to variability within groups. 

• Selection effects- when the kinds of participants in one level of the independent variable are systematically different from those in the other 

  • Also when experimenters let participants choose which group they want to be in 

  • If they assign one type of person to one condition, and another type of person to another condition 

• Variables p 281 

• Differences between independent groups and within subjects designs 

  • Independent- separate groups of participants are placed into different levels of the independent variable- between subjects or between groups 

  • Within groups design- each person is presented with all levels of the independent variable 

  • Two basic forms- posttest only design and the pretest/posttest design 

• Posttest only design- equivalent groups, posttest only design 

  • Participants are randomly assigned to independent variable groups and are tested on the dependent variable once 

• Pretest/posttest design- participants randomly assigned to at least two groups and are tested on the key dependent variable twice, once before and once after exposure to the independent variable 

• How experiments establish causality 

  • P 284-285 

• Counterbalancing 

  • P 300-301, in class handout 

  • Present the levels of the independent variable to participants in different sequences 

  • Any order effects should cancel each other out when all the data are combined 

  • Full counterbalancing- all possible condition orders are represented 

  • Partial counterbalancing- only some of the possible condition orders are represented- present the conditions in a randomized order for every subject 

• Confidence intervals 

  • P 309-310, 351 

Ch 11 

• Threats to validity in experiments and how to address them 

  • P 324-339, 351-352, table 11.1 

  • Maturation- a change in behavior that emerges more or less spontaneously over time 

  • Regression to the mean- regress to the mean 

  • Selection bias haven't randomly assigned pple to groups 

  • Attrition when a systematic type of participant drops out of the study before it ends 

  • Confounding variables- bad design 

  • History- result forma historical or external factor that systematically affects most members of the treatment group at the same time as the treatment received 

  • Instrumentation error- when a measuring instrument changes over time 

  • Testing effects- scores change over time just because participants have taken the test more than once 

  • Demand characteristic- participants guess the study's purpose and change their behavior 

• Threats to external validity- sample selection, situational factors, generalizability 

• Bad designs  

  • P 325 

  • One group, pretest, posttest design 

  • Recruits one group, measures them on a pretest, exposes them to rteatment, measures on a posttest 

  • No comparison group 

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Ch 12 

• Main effects 

  • P 373-374, 386-389, 391 

  • Overall effect of one independent variable on the dependent variable, averaging over the levels of the other independent variable 

  • In a design with two independent variables, there are two main effects 

• Identifying interactions 

  • P 365-367,375-378, 386-389 

  • Interaction effect- whether the effect of the original independent variable depends on the level of another independent variable depends on the level of another independent variable 

  • An interaction of two independent variables allows researchers to establish whether or not it depends 

  • A difference in differences 

• Factorial notation 

  • P 383-385, 391 

  • Two or more independent variables 

  • Researchers cross two independent variables 

  • One independent variable is manipulated as independent groups 

• Mixed designs 

  • P 383 

  • Quasi independent variable- researchers do not have full experimental control over the independent variable 

  • Nonequivalent control group posttest only design- participants were not randomly assigned to groups and were tested only once, after exposure to one level of the independent variable or the other 

  • Nonequivalent control group pretest/posttest design- participants not randomly assigned to groups and were tested before and after some intervention