Research Methods in Health Psychology

Chapter 2

Science

• Science is not a thing in and of itself. It is a set of methods used to understand natural phenomena with the goals of:– Explanation– Prediction– Control

Assumptions of Science

• Naturalism– If its real it can be measured

• Empiricism– Relying on or derived from

observation or experiment– Verifiable or provable by means of

observation or experiment

Its About the Data

• Idiographic refers to the individual.• Nomothetic - Of or relating to the

study or discovery of general scientific laws.

• When we use nomothetic data we lose specificity to the individual but we gain in that we can now generalize to others.

Levels of AnalysisLevels of Analysis

Behavioral/PsychologicalBehavioral/Psychological

Organ SystemsOrgan Systems

MolecularMolecular

CellularCellular

Social/Historical/EnvironmentalSocial/Historical/Environmental

Levels of Rigor of Scientific Data

• Naturalistic Observation– Case Study

• Correlation– Most of psychological research– Quasi-experimental

• Experimental Method– The gold standard

Experimental Method • Involves direct

controlled manipulation– Independent variable– Dependent variable

• Two or more groups– experimental group– control group

• Random assignment

Independent Variable

• Under control of the experimenter• Used to explain changes in the

dependent variable• Example: Cold virus up the nose

– Cold Virus Exposure (Virus, Placebo, Control)

– Stress (hi, low, none)

Dependent Variable

• Not under control by the experimenter

• Presumed to be caused or affected by the independent variable

• Example: getting a cold – number of cold symptoms

Random Assignment

• Random Assignment– Allows us to control for all potential

confounds– Each subject has an equal chance of

being in each group. – Intact groups not random– Replication to deal with chance

variation

Epidemiology

Epidemiology

• Branch of medicine that investigates the frequency and distribution of disease and related factors.

John Snow• The first modern

epidemiologist (1854):– Mapping cases of

cholera and household use of water sources revealed pattern involving a single water pump

• Removing the handle from the Broad Street pump ended the epidemic.

Epidemiology - Terms• Prevalence-the

proportion of the population that has a particular disease at a specific time.

• Incidence-measures the frequency of new cases of the disease.

Epidemiology - Terms

• Mortality- Death rate• Morbidity-The rate of

prevalence/incidence of a disease.

Epidemiology – Ultimate Goals

• Determine the etiology or origins of a specific disease. To develop and test hypotheses.

• Discovering who is more likely to have a disease is useful in determining its cause.

• Discovering risk factors such as dirty water or smoking.

Epidemiology

• A risk factor is any characteristic or condition that occurs with greater frequency in people with a disease than it does in people free from the disease.

Epidemiology

• Relative versus absolute risk.Relative: Considered in comparison with something else

• Relative risk the ratio of incidence or prevalence in the exposed group to that of the unexposed group

• Absolute risk-The persons chances of developing a disease.

Example: Alameda County Study

• Started in 1965

Epidemiology - Causation• Typically, ER is correlational• Certain criteria can be established to assert a

causal relationship– Well-designed studies– The direction for the relationship is risk condition – Dose-response relationship exists between risk

factor and condition– A direct, consistent association between an independent

variable, such as a behavior, and a dependent variable, such as a disease.

– When the risk is removed the probability of disease is reduced

– Causality is plausible– Animal studies support a causal link