PUBH 475 Week 6 INternal Validity and Quantitative Study Designs

What are the two types of data collection methods?

Primary and secondary.

What is the difference between cross-sectional and longitudinal data collection?

Cross-sectional collects data at one point in time, while longitudinal collects data at two or more points.

What is the relationship between independent and dependent variables?

Independent variables (IV) are manipulated to observe their effect on dependent variables (DV).

What type of relationship does causation imply?

Causation implies that one variable directly affects another (X -> Y).

How many data points are needed to establish causation?

Two or more data points are needed for causation.

Which study design is associated with temporal ambiguity?

Cross-sectional studies are associated with temporal ambiguity because they measure exposure and outcome at one point in time, making it unclear which came first.

Laboratory Research experiments

easier to manipulate the IV's and control experimental conditions. Can use one data collection point to est. causality because its more controlled.

Field Research

takes place in a natural setting. more of a challenge to manipulate IV's and control experimental conditions. Need at least two data collection points to establish causality. Harder to achieve internal validity bc of so many extraneous variables.

What is internal validity concerned with?

Internal validity is whether the observed effects of the independent variable on the dependent variable are real and not caused by extraneous variables. Concerned with how good the research design is. a study that does a good job controlling for possible effects of extraneous variables on the dependent variables has good vinternal validity.

What are threats to internal validity?

Threats include history, maturation, testing, instrumentation, people, selection bias, attrition, Hawthorne effect, placebo effect, diffusion/treatment effect, location, and implementation effect.

History

time passing, events that happen during a study can affect the results.

Maturation

biological process of aging. You want to ask questions of participants age to address threat.

Testing

constant data collection waves (O) may change performance due to familiarity with the tests. Participants might get overwhelmed/might not be honest with responses.

Instrumentation

Tools we use to collect data from participants. Measures: if the way a variables is measured changes over tome it can affect the results. People: changes in observers or test administrators

Selection bias

in an experiment, unintended differences between the participants in different groups

Attrition

loss of participants due to dropouts or death

What is the Hawthorne effect?

occurs when participants change their behavior because they know they are being studied.

Placebo effect

experimental results caused by expectations alone. any effect on behavior caused by the administration of an inert substance or condition, which the recipient assumes is an active agent.

diffusion/treatment effect

when participants in experimental and control group share info or interact affecting results

Location

when differences in study setting influence results

implementation effect/fidelity

when differences in how the study is conducted (by researchers) affects the results

What is random assignment in research?

Random assignment is the process of assigning study participants to groups where each has an equal chance of being assigned to either treatment or control. Importance: distributes bias across conditions, investigators cannot choose assignment, ideally groups should be similar in demographics factors

What are the three main quantitative study designs?

Experimental, quasi-experimental, and non-experimental.

What distinguishes experimental designs from quasi-experimental designs?

Experimental designs involve random assignment and manipulation of the independent variable, while quasi-experimental designs manipulate the IV without random assignment.

Non-experimental

IV is not manipulated, no random assignment, all other quantitative research/epi studies

Pre-experimental designs

A pre-experimental design is a weak study design that lacks a WEAK group and baseline data, making it difficult to establish causation.

One shot case study

pre-experimental design. X O. weakness: weakness: no baseline, we dont know if changes occurred due to the intervention or if they were already present. No control group, cant establish causation. Strengths: cheap, quick, applicable in cases where pre-testing isn't possible (disaster response evaluation

one-group pretest-posttest design

pre-experimental design. O1 X O2. 2 observations, 1 group. strengths: baseline weakness: no control, maturation, testing effect, history

static group comparison

pre-experimental design. X___O___

…………… O

A design that compares two groups, one receiving treatment and one as a control, but lacks randomization. both measured posttest.

posttest-only control group design

true experiment design. R X O

R O

only measures outcome after intervention

Pretest-posttest control group

R O1 X O2

R O1 O2

most feasible/practicle. weakness: testing effect, attrition. strengths: control,baseline, follow up, randomization

Solomon Four-Group

R O1 X O2 (treatment)

R O1 O2 (control)

R X O (treatment)

R O (control)

strongest study design against internal validity. expensive

interrupted time series design

O1 O2 O3 O4 X O5 O6 O7 O8

A quasi-experimental design that collects multiple observations before and after an intervention. strength: a lot of data weakness; expensive

Nonequivalent Control group

_O1_ X_O2_

O1 O2

non comparable (_ _ )

not random. strength: pre and post test, and control