Forward looking

backward looking

looking at simultaneous events

a form of sampling where a representative group of research participants is selected from a larger group by chance.

a procedure used in experiments to create multiple study groups that include participants with similar characteristics so that the groups are equivalent at the beginning of the study.

occurs when the way a study is designed or carried out causes an error in the results and conclusions.

called experiments or clinical trials. They provide stronger evidence than observational studies.

simply a descriptive account of interesting characteristics observed in a group of patients.

simply a descriptive account of interesting characteristics observed in a group of patients.

with the disease or outcomes

without the disease or outcomes

prevalence study

studies analyze data collected on a group of subjects at one time

Subjects are selected and information is obtained in a short period of time.

a group of people who have something in common and who remain part of a group over an extended time.

Subjects are selected by some defining characteristics suspected of being a risk factor for a disease or health effect.

Are studies in which experimental drug or procedure is compared with another drug or procedure, sometimes a placebo and sometimes and sometimes the previously accepted treatment.

Is the epitome of all research designs because it provides the strongest evidence for concluding causation; it provides the best insurance that the result was due to the intervention.

Subjects are not always randomized to treatment options.

Referred simply as clinical trial or comparative study, with no mention of randomization.

highly questionable

uses published information from other studies and combines the results so as to permit an overall conclusion.

similar to review articles, but additionally includes a quantitative assessment and summary of the findings