Chapter 2 Research Methods

crossover study

A clinical trial in which each group of subjects receives two or more treatments, but in different sequences.

double-blind trial

A clinical trial in which neither the subjects nor the investigator(s) know which treatment subjects have received.

historical cohort study

A cohort study that uses existing records or historical data to determine the effect of a risk factor or exposure on a group of patients.

experiment (in probability)

A planned process of data collection.

representative population (or sample)

A population or sample that is similar in important ways to the population to which the findings of a study are generalized.

cross-validation

A procedure for applying the results of an analysis from one sample of subjects to a new sample of subjects to evaluate how well they generalize. It is frequently used in regression

cost-benefit analysis

A quantified methods to evaluate the trade-offs between the costs (or disadvantages) and the benefits (or advantages) of a procedure or management strategy.

cost-effectiveness analysis

A quantitative method to evaluate the cost of a procedure or management strategy that takes into account the outcome as well in order to select the lowest-cost option.

case-series study

A simple descriptive account of interesting or intriguing characteristics observed in a group of subjects.

MEDLINE

A system that permits search of the bibliographic database of all articles in journals included in Index Medicus. Articles that meet specific criteria or contain specific key words are extracted for the researcher's perusal

controlled trial

A trial in which subjects are assigned to a control condition as well as to an experimental condition.

uncontrolled study

An experimental study that has no control subjects.

concurrent controls

Control subjects assigned to a placebo or control condition during the same period that an experimental treatment or procedure is being evaluated.

PUBMED

See MEDLINE.

nonrandomized trial

A clinical trial in which subjects are assigned to treatments on other than a randomized basis. It is subject to several biases.

experimental study

A comparative study involving an intervention or manipulation. It is called a trial when human subjects are involved.

cohort

A group of subjects who remain together in the same study over time.

functional status

A measure of a person's ability to perform his or her daily activities, often called activities of daily living.

quality of life (QOL)

A measure of a person's subjective assessment of the value of his or her health and functional abilities.

meta-analysis

A method for combining the results from several independent studies of the same outcome so that an overall P value may be determined.

prospective study

A study designed before data are collected.

self-controlled study

A study in which the subjects serve as their own controls, achieved by measuring the characteristic of interest before and after an intervention.

longitudinal study

A study that takes place over an extended period of time.

retrospective study

A study undertaken in a post hoc manner, ie, after the observations have been made.

randomized controlled trial (RCT)

An experimental study in which subjects are randomly assigned to treatment groups.

blind study

An experimental study in which subjects do not know the treatment they are receiving; investigators may also be blind to the treatment subjects are receiving; see also double-blind trial.

cohort study

An observational study that begins with a set of subjects who have a risk factor (or have been exposed to an agent) and a second set of subjects who do not have the risk factor or exposure. Both sets are followed prospectively through time to learn how many in each set develop the outcome or consequences of interest.

case-control

An observational study that begins with patient cases who have the outcome or disease being investigated and control subjects who do not have the

cross-sectional study

An observational study that examines a characteristic (or set of characteristics) in a set of subjects at one point in time; a "snap-shot" of a characteristic or condition of interest; also called survey or poll.

control subjects

In a clinical trial, subjects assigned to the placebo or control condition; in a case-control study, subjects without the disease or outcome.

historical controls

In clinical trials, previously collected observations on patients that are used as the control values against which the treatment is compared.

patient satisfaction

Refers to outcome measures of patient's liking and approval of health care facilities and operations, providers, and other components of the entities that provide patient care.

retrospective cohort study

See historical cohort study.

quartile

The 25th percentile or the 75th percentile, called the first and third quartiles, respectively

matching (or matched groups)

The process of making two groups homogeneous on possible confounding factors. It is sometimes done prior to randomization in clinical trials.

prevalence

The proportion of people who have a given disease or condition at a specified point in time. It is not truly a rate, although it is often incorrectly called prevalence rate.

distribution

The values of a characteristic or variable along with the frequency of their occurrence. Distributions may be based on empirical observations or may be theoretical probability distributions (eg, normal, binomial, chi-square).

intervention

the maneuver used in an experimental study. It may be a drug or a procedure.