Chapter 10 Finding Relationships Among Variables: Non-Experimental Research Non-experimental research Non-experimental approaches are used when the researcher is unable to control the variables or the nature of the question is not causal. In general, a non-experimental design includes research where: – the researcher does not manipulate an IV, – has limited or no control over the nature or timing of the treatment, or – when causal relationships are not the primary focus of the research. Quasi experiments Quasi experiments – Designs that look a lot like true experiments and that are statistically analyzed in similar ways. – The researcher can compare groups but does not control the nature and/or the timing of the treatment or comparison variable. Or the treatment may be a participant variable. – Causal interpretations cannot be made. Participant variables – variables associated with the participants themselves (e.g.. gender, a treatment the participant chose). Time series designs Time series design – A quasi-experimental design where participants who have been exposed to a treatment are tested both before and after the introduction of that treatment. – The researcher does not control the nature of the treatment or the time that it was introduced. – Usually involves several pre and posttest measures and may include a comparison group; both are methods to try to control extraneous variables. Time series designs Interrupted time series design – The researcher takes several pretest measures and several posttest measures. – Measuring behavior at different times allows us to determine the natural fluctuation in scores and better assess any post treatment changes. – Because there is no control group, we can’t tell if something else was responsible for the changes in scores (other than the treatment). Time series designs Multiple time series design – Like an interrupted time series design but includes a control group that was not exposed to the treatment. – Even with a control group be cautious about interpretations. An alternative explanation may explain the outcome (i.e.. the outcome may not have resulted because of the treatment). Non-equivalent groups designs Non-equivalent groups designs – Used when researchers want to compare groups that they know, or suspect, are different at the outset of the study. – Compares changes in behavior between the groups. – By comparing changes you control for initial group differences. Longitudinal research Longitudinal research – Involves studying a group of individuals over a long period of time to determine how characteristics measured earlier in life relate to behavior later in life. – Difficult and expensive to conduct. – Attrition (loss of participants) can be a major problem and may effect the internal validity of the study. Cross-sectional research Cross-sectional research – Used to study groups of people who are different ages. – Cohort effect – variables that are confounded with age. Sequential research – Combines cross-sectional and longitudinal research by selecting a cross section of ages over a number of years. Cohort effects are controlled by following a number of age cohorts (cross-sectional) over time (longitudinal). Cross-sectional research Microgenetic method – Involves carefully observing behavior during periods when rapid change is occurring and collecting both quantitative and qualitative information. – Used to study the process of change. Case studies Case studies – In depth studies of a single individual. – Used when a researcher is interested in studying a single individual on many variables and is not assessing a treatment. – The objective is to describe the characteristics of the individual case, not to generalize to a population of similar cases. – Often qualitative, but can be more quantitative. Correlational research Correlational research – Used to study relationships between variables. – Variables that are systematically related are said to be correlated. – Often used to research topics that would otherwise be unethical to study. – Correlation does not infer causation! – Confounding variables may affect the results. Correlational research Multiple regression – A powerful technique that allows us to look at the relationship between a number of predictor variables and a single criterion variable. – Results tell us if the predictor variables are positively or negatively correlated with the criterion variable. Also shows the relative importance of each variable in determining behavior.