longitudinal study

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study

 [stud´e]
a careful examination of a phenomenon; see also design.
cohort study prospective study.
cross-sectional study one employing a single point of data collection for each participant or system being studied. It is used for examining phenomena expected to remain static through the period of interest. It contrasts with a longitudinal s.
electrophysiological s's (EPS) studies from within the heart of its electrical activation and response to electrical stimuli and certain drugs. In general they include intravenous and/or intra-arterial placement of one or more electrode catheters at sites in the atria, ventricles, or coronary sinus, and sometimes the pulmonary artery or aorta. They record activity or stimulate the heart at various rates and cadences and are aids in the evaluation of electrophysiologic properties such as automaticity, conduction, and refractoriness. They also initiate and terminate tachycardias, map the sequence of activation, and aid in evaluation of patients for various forms of therapy and for the response to therapy. During these studies catheter ablation procedures, such as radio frequency ablation and electrical ablation, may be performed.
flow study uroflowmetry.
longitudinal study one in which participants, processes, or systems are studied over time, with data being collected at multiple intervals. The two main types are prospective studies and retrospective studies. It contrasts with a cross-sectional s.
pilot study a smaller version of a proposed research study, conducted to refine the methodology of the later one. It should be as similar to the proposed study as possible, using similar subjects, the same setting, and the same techniques of data collection and analysis.
prospective study an epidemiologic study in which the groups of individuals (cohorts) are selected on the bases of factors that are to be examined for possible effects on some outcome. For example, the effect of exposure to a specific risk factor on the eventual development of a particular disease can be studied. The cohorts are then followed over a period of time to determine the incidence rates of the outcomes being studied as they relate to the original factors in question. Called also cohort study.



The term prospective usually implies a cohort selected in the present and followed into the future, but this method can also be applied to existing longitudinal historical data, such as insurance or medical records. A cohort is identified and classified as to exposure to the risk factor at some date in the past and followed up to the present to determine incidence rates. This is called a historical prospective study, prospective study of past data, or retrospective cohort study.
retrospective study an epidemiologic study in which participating individuals are classified as either having some outcome (cases) or lacking it (controls); the outcome may be a specific disease, and the persons' histories are examined for specific factors that might be associated with that outcome. Cases and controls are often matched with respect to certain demographic or other variables but need not be. As compared to prospective studies, retrospective studies suffer from drawbacks: certain important statistics cannot be measured, and large biases may be introduced both in the selection of controls and in the recall of past exposure to risk factors. The advantage of the retrospective study is its small scale, usually short time for completion, and its applicability to rare diseases, which would require study of very large cohorts in prospective studies. See also prospective s.
urinary flow study uroflowmetry.
voiding pressure study simultaneous measurement of bladder contraction, urinary flow, and sphincter electromyogram.

lon·gi·tu·di·nal stud·y

a study of the natural course of life or disorder in which a cohort of subjects is serially observed over a period of time and no assumptions need be made about the stability of the system.
Synonym(s): diachronic study

longitudinal study

An epidemiologic study that follows a population forward over time, evaluating the effects of one or more variables on a process. If individuals are followed, it is termed a longitudinal cohort study. If classes—e.g., age classes—are studied, it is a longitudinal cross-sectional study. Longitudinal studies are the converse of horizontal studies.
 
Examples
Cohort studies; case-control studies; Framingham Study in Massachusetts, US; Port Pirie study, an ongoing analysis of the long-term effects of blood lead levels on IQ.

longitudinal study

Diachronic study Statistics A study that follows the same persons over time, evaluating the effects of one or more variables on a processtime Examples Cohort studies, case-control studies. Cf Cross-sectional study, Horizontal study.

lon·gi·tu·di·nal stud·y

(lonji-tūdi-năl stŭdē)
A study of the natural course of life or disorder in which a cohort of subjects is serially observed over a period of time and no assumptions need be made about the stability of the system.

longitudinal study

a chronological study in epidemiology which attempts to establish a relationship between an antecedent cause and a subsequent effect. See also cohort study.
References in periodicals archive ?
Table 8 shows the distribution by establishment size class, categorizing establishments in the longitudinal sample by their size when they last responded.
As shown in Table 2, the original group of 670 students fell into three groups at Time 2: the 147 students in the Longitudinal sample who completed both the Time 1 and Time 2 surveys, 393 students who had taken the Time 1 survey and were still at the university but did not respond to our invitations to complete the Time 2 survey, and a third group of 130 students who completed the Time 1 survey but were no longer enrolled at the university or could not be contacted because of inadequate identifiers.
In this study, we found gender similarities in performance on standardized math tests in a national, longitudinal sample of students from middle school through high school.
The hypothesis was tested in the longitudinal sample using a repeated measures multiple analysis of variance.
The second criterion, discrepancy benchmark criteria, was a W score at or above the mean of the longitudinal sample at the end of grade 1 on both the Word Attack and Passage Comprehension subtests in English of the WLPB-R and a raw score for words correctly read per minute on an appropriate DIBELS ORF passage that was at or above the mean of the longitudinal sample.
This occurs when underrepresentation of one or more groups in the longitudinal sample leads to correlations between variables that diverge from true correlations in the original sample.
Khwaja uses microdata on a longitudinal sample of individuals from the Health and Retirement Study and conducts a computer- simulated thought experiment comparing the trends and outcomes under the status quo to a world without Medicare.
In this longitudinal sample, a number of students had only two different Holland types over the time span studied, and these types were consistent (i.
Participants in the longitudinal sample were in the pretransplant assessment phase and were expected to be activated to the transplant waiting list or were waiting for a living donor transplant.
4) RHS is a random longitudinal sample of 11,000 household heads, between the ages of 58 and 63 in 1969, interviewed biennially through 1979.
In the next to the last section, the production model is estimated on a much larger longitudinal sample (state data), which allows for more variation in the benefits replacement rate, the key independent variable of interest in the analysis.
The present study will test these rival hypotheses by considering potential variations in entry, continuous stayer, and reentry statuses and associated likelihoods by differences in levels of educational attainment for a national longitudinal sample of women.

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