Ch.3 Research Methods and Study Design

Experimental Design: a technical term for a specific type of research, experimental design is used to determine causation and rule out other possible explanations rather than correlation.

Experimental Design

1) select the population

-low cost

-easy access

-not “all humans”

-results only apply to population in the study

-other populations are outside the scope of the experiment

Experimental Design

1) Select the population

2) Operationalize the independent and dependent variables

-independent variable is manipulated by the research team

-dependent variable is the variable that is measured.

-the dependent variable measured must be quantitative or numerical, not qualitative, because the dependent variable is used to conduct statistical analysis that will test the research hypothesis.

-to qualify for an experimental design, researchers need to have maximum control over the experimental environment, so that they can be measured.

-reproducibility: good experimental design requires experiments that can be reproduced by other researchers.

-operational definition: a specification of what researchers mean by each variable.

Experimental Design

1) Select the population

2) Operationalize the independent and dependent variables

3) Carefully select the control and experimental groups

-control group: group that acts as a point of reference or comparison

-experimental groups: group of participants that receive treatment

-homogenous control groups: groups that are the same throughout, as similar as possible to the experimental group, except for the variable of interest (the goal of the homogenous control group is to rule out confounding variables) (confounding variables are outside influence that confuses or invalidates an observation)

-to optimize study design, experimental and control groups must be as similar as possible to limit confounding variables

-Placeblo effect: a patient’s symptoms improve after receiving fake treatment, just believing the treatment is being administered leads to a measurable result. (placebo effects are countered by “double blind”: a research method where neither the participants nor the researchers know who is receiving the active treatment (such as a new drug) and who is receiving a dummy treatment (such as a placebo) until the experiment is completely over).

-to optimize study design, experimental and control groups must be as similar as possible to limit confounding variables

-researchers can never account for every potential extraneous variable

Experimental Design

1) Select the population

2) Operationalize the independent and dependent variables

3) Carefully select the control and experimental groups

4) Randomly sample from the population

-sampling should be random

-it should be equally likely for any member of the population to be a participant

-most common flaw in social research is mot studied are done on undergraduate students and then results are applied to the greater population

-selection bias: a general category in systemic flaws in a design that can compromise results.

-sampling bias: some members of a target population have a lower or higher chance of being selected than others. Sampling bias a type of selection bias.

-meta-analysis: big-picture “meta” analysis of many studies to look for trends in data

-attrition: “rubbing against” attrition is when participants who drop out systematically differ from those who remain. A gradual reduction in sample size, a type of selection bias.

Experimental Design

1) Select the population

2) Operationalize the independent and dependent variables

3) Carefully select the control and experimental groups

4) Randomly sample from the population

5) randomly assign individuals to groups

-after individuals have been incentivized, it’s time to randomly assign them to the experimental and control groups

-well designed experiments have it equally likely that people are assigned to either group.

-randomized block technique: used to ensure study groups have equal sample sizes at regular intervals (participants are divided into small, ordered blocks and randomly assigned so that each treatment is equally represented within every block.

Experimental Design

1) Select the population

2) Operationalize the independent and dependent variables

3) Carefully select the control and experimental groups

4) Randomly sample from the population

5) randomly assign individuals to groups

6) measure the results

-make sure the results are valid

-the dependent variable is quantitiative (and therefore measurable)

-instruments used are reliable. Reliability means stable and consistent results are produced, measure what they’re supposed to (known as construct validity) and that repeated measurements lead to similar results (known as replicability).

-Construct validity: the extent to which a test, survey, or experimental tool accurately measures what it’s supposed to.

-Replicability: repeated measurements lead to similar results.

-psychometrics: is the study of how to measure psychological variables through testing.

-Response bias: the systematic tendency of participants to answer survey or interview questions inaccurately, untruthfully, or in a distorted manner