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Glossary of terms used in health research - L

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  • L'AbbĂ© plot
    • A scatter plot of the risk in the experimental group against the risk in the control group. Ideally the size of the plotting symbols should be proportional to the size of the trials. Trials in which the experimental treatment had a higher risk than the control will be in the upper left of the plot, between the y axis and the line of equality. If experimental is no better than control then the point will fall on the line of equality, and if the control treatment has a higher risk than the experimental treatment then the point will be in the lower right of the plot, between the x axis and the line of equality.
  • Laboratory manual
    • Laboratory manuals [MeSH - publication type]: works containing concise background information and directions for activities, including conducting experiments or diagnostic tests in the laboratory.
  • Language bias
    • The systematic error introduced when the search of potential studies to be included in a meta-analysis is focused, in general, in one language (mainly English). Given that studies published in English are more widely read, it is possible that significant results of studies carried out in non-English countries are more published in English journals than in journals written in other languages.
  • Latency period
    • Wikipedia
      A period of subclinical or inapparent pathologic changes following exposure, ending with the onset of symptoms of chronic disease.
  • Lay knowledge
    • Lay knowledge refers to the understanding that members of the lay public bring to an issue or problem.
  • Lead time
    • Wikipedia
      The length of time between the detection of a disease (usually based on new, experimental criteria) and its usual clinical presentation and diagnosis (based on traditional criteria).
  • Lead time bias
    • Wikipedia
      The bias that occurs when two tests for a disease are compared, and one test (the new, experimental one) diagnoses the disease earlier, but there is no effect on the outcome of the disease-- it may appear that the test prolonged survival, when in fact it only resulted in earlier diagnosis when compared to traditional methods. It is an important factor when evaluating the effectiveness of a specific test.
  • Lecture
    • Wikipedia
      Oral presentation intended to present information or teach people about a particular subject, for example by a university or college teacher.
      Speech read or delivered before an audience or class, especially for instruction or to set forth some subject.
      Lectures [MeSH - publication type]: works consisting of speeches read or delivered before an audience or class, especially for instruction or to set forth some subject. They are differentiated from addresses [publication type] which are less didactic and more informational, entertaining, inspirational, or polemic.
  • Lecture notes
    • Notes taken at the delivery or reading of a speech before an audience or class, usually given to instruct.
      Lecture notes [MeSH - publication type]: works consisting of notes taken at the delivery or reading of a speech before an audience or class, usually given to instruct.
  • Legally acceptable representative
    • An individual or juridical or other body authorized under applicable law to consent, on behalf of a prospective subject, to the subject's participation in the clinical trial.
  • Legislation
    • MeSH - Wikipedia
      Legislation (or "statutory law") is law which has been promulgated (or "enacted") by a legislature or other governing body, or the process of making it.
      The enactment of laws and ordinances and their regulation by official organs of a nation, state, or other legislative organization. It refers also to health-related laws and regulations in general or for which there is no specific heading.
      Legislation [MeSH - publication type]: works consisting of the text of proposed or enacted legislation that may be in the form of bills, laws, statutes, ordinances, or government regulations.
  • Length time bias
    • Wikipedia
      A form of selection bias, a statistical distortion of results which can lead to incorrect conclusions about the data. Length time bias can occur when the lengths of intervals are analyzed by selecting intervals that occupy randomly chosen points in time or space. This process favors longer intervals, thus skewing the data. For example, length time bias can affect data on screening tests for cancer. Faster-growing tumors generally have a shorter asymptomatic phase than slower-growing tumors, and so are less likely to be detected. However, faster-growing tumors are also often associated with a poorer prognosis. Slower-growing tumors are hence likely to be over-represented in screening tests. This can mean screening tests are erroneously associated with improved survival, even if they have no actual effect on prognosis.
  • Letter
    • Letter [MeSH - publication type]: work consisting of written or printed communication between individuals or between persons and representatives of corporate bodies. the correspondence may be personal or professional. in medical and other scientific publications the letter is usually from one or more authors to the editor of the journal or book publishing the item being commented upon or discussed. letter is often accompanied by comment.
  • Levels of evidence
    • Wikipedia
      A ranking system used to describe the strength of the results measured in a clinical trial or research study. The design of the study (such as a case report for an individual patient or a randomized double-blinded controlled clinical trial) and the endpoints measured (such as survival or quality of life) affect the strength of the evidence.
      Levels of evidence refer to a hierarchy of study designs that have been grouped according to their susceptibility to bias. The hierarchy indicates which studies should be given most weight in an evaluation where the same question has been examined using different types of study.
  • Life expectancy
    • MeSH - Wikipedia
      Life expectancy is the expected (in the statistical sense) number of years of life remaining at a given age.
      The number of years of life that can be expected on average in a given population.
      A figure representing the number of years, based on known statistics, to which any person of a given age may reasonably expect to live.
  • Life expectancy at birth
    • Average number of years that a newborn is expected to live if current mortality rates continue to apply. WHO computes life expectancy at birth from a period life table.
      The average number of years that a newborn could expect to live, if he or she were to pass through life exposed to the sex- and age-specific death rates prevailing at the time of his or her birth, for a specific year, in a given country, territory, or geographic area.
  • Life skills
    • Wikipedia
      Abilities for adaptive and positive behavior that enable individuals to deal effectively with the demands and challenges of everyday life.
  • Life skills programs
    • Wikipedia
      Interventions that implement the concept of life skills. Life skills refers to a large group of psychosocial and interpersonal skills which can help people make informed decisions, communicate effectively, and develop coping and self-management skills that may help them lead a healthy and productive life. Life skills commonly include components that focus on social skills, personal skills and knowledge and also resistance skills. Life skills based interventions are often classified as part of the broader category of social influence based interventions.
  • Life span
    • Wikipedia
      The maximum age that human beings could reach under optimum conditions.
  • Life style
    • MeSH
      Typical way of life or manner of living characteristic of an individual or group.
  • Life table
    • MeSH - Wikipedia
      In actuarial science, a life table (also called a mortality table or actuarial table) is a table which shows, for each age, what the probability is that a person of that age will die before their next birthday.
      A tabular display of life expectancy and the probability of dying at each age (or age group) for a given population, according to the age-specific death rates prevailing at that time. The life table gives an organized, complete picture of a population's mortality.
      A set of tabulations that describe the probability of dying, the death rate and the number of survivors for each age or age group. Accordingly, life expectancy at birth is an output of a life table.
      Summarizing techniques used to describe the pattern of mortality and survival in populations. These methods can be applied to the study not only of death, but also of any defined endpoint such as the onset of disease or the occurrence of disease complications.
  • Likelihood functions
    • MeSH
      Functions constructed from a statistical model and a set of observed data which give the probability of that data for various values of the unknown model parameters. Those parameter values that maximize the probability are the maximum likelihood estimates of the parameters.
  • Likelihood ratio of a negative test
    • Wikipedia
      Ratio of the probability of a false negative result if the disease is present to the probability of a true negative result if the disease is absent.
  • Likelihood ratio of a positive test
    • Wikipedia
      Ratio of the probability of a true positive result if the disease is present to a false positive result if the disease is absent.
  • Likelihood ratios in diagnostic testing
    • Wikipedia
      In evidence-based medicine, likelihood ratios are used for assessing the value of performing a diagnostic test. They use the sensitivity and specificity of the test to determine whether a test result usefully changes the probability that a condition (such as a disease state) exists.
  • Likert format
    • Wikipedia
      A format for closed-response questions used to elicit attitudes of the respondents to a certain statement. The respondent chooses from among five categories: strongly agree, agree, undecided, disagree, strongly disagree.
  • Likert scale
    • Wikipedia
      Psychometric scale commonly used in questionnaires, and is the most widely used scale in survey research, such that the term is often used interchangeably with rating scale even though the two are not synonymous. When responding to a Likert questionnaire item, respondents specify their level of agreement to a statement.
  • Limit of detection
    • MeSH - Wikipedia
      In analytical chemistry, the detection limit, lower limit of detection, or LOD (limit of detection), is the lowest quantity of a substance that can be distinguished from the absence of that substance (a blank value) within a stated confidence limit (generally 1%).
      Concentration or quantity that is derived from the smallest measure that can be detected with reasonable certainty for a given analytical procedure.
  • Linear models
    • MeSH
      Statistical models in which the value of a parameter for a given value of a factor is assumed to be equal to a + bx, where a and b are constants. The models predict a linear regression.
  • Linear regression
    • Wikipedia
      The term used for a regression analysis when the dependent or target variable is a continuous variable, and the relationship between the dependent and independent variables is thought to be linear.
  • Linear scale
    • A scale that increases in equal steps. In a linear scale on a RevMan forest plot, the distance between 0 and 5 is the same as the distance between 5 and 10, or between 10 and 15. A linear scale may be used when the range of numbers being represented is not large, or to represent differences.
  • Linkage and exchange strategies
    • Linkage and exchange strategies refer to initiatives that seek to promote research utilization in decision contexts, and encourage research that generates purposeful and useful evidence.
  • Literacy rate
    • The proportion of the adult population aged 15 years and over which is literate, expressed as a percentage of the corresponding population, total or for a given sex, in a given country, territory, or geographic area, at a specific point in time, usually mid-year. For statistical purposes, a person is literate who can with understanding both read and write a short simple statement on his/her everyday life.
  • Literature review
    • MeSH - Wikipedia
      A literature review is a body of text that aims to review the critical points of current knowledge and or methodological approaches on a particular topic.
      A summary and explanation of key studies relevant to a proposed project.
      Published materials which provide an examination of recent or current literature. Review articles can cover a wide range of subject matter at various levels of completeness and comprehensiveness based on analyses of literature that may include research findings. The review may reflect the state of the art. It also includes reviews as a literary form.
  • Live birth
    • MeSH - Wikipedia
      Live birth in the tenth revision of the International Statistical Classification of Diseases and Related Health Problems (ICD 10) is defined as the complete expulsion or extraction from its mother of a product of conception, irrespective of the duration of the pregnancy, which, after such separation, breathes or shows any other evidence of life such as heartbeat, umbilical cord pulsation, or definite movement of voluntary muscles, whether the umbilical cord has been cut or the placenta is attached.
      The event that a fetus is born alive with heartbeats or respiration regardless of gestational age. Such liveborn is called a newborn infant (infant, newborn).
  • Local consensus process
    • A strategy for changing clinician behavior. Inclusion of participating clinicians in discussions to create agreement with a suggested approach to change provider practice.
  • Local opinion leaders
    • A strategy for changing clinician behavior. These persons are clinician peers who are recognized by their colleagues as model caregivers or who are viewed as having particular content expertise.
  • Logarithmic scale
    • Wikipedia
      A scale in which the logarithm of a value is used instead of the value. In a logarithmic scale on a RevMan forest plot, the distance between 1 and 10 is the same as the distance between 10 and 100, or between 100 and 1000. A logarithmic scale may be used when the range of numbers being represented is large, or to represent ratios.
  • Logic model
    • Wikipedia
      A logic model is a graphic representation of a program that describes the program’s essential components and expected accomplishments and conveys the logical relationship between these components and their outcomes.
  • Logic of evidence based practice
    • The logic of evidence based practice identifies a cyclic relation between evaluation, evidence, practice, and further evaluation. It is based on the premise that evaluations determine whether anticipated intervention effects occur in practice, and identify unanticipated effects.
  • Logistic models
    • MeSH
      Statistical models which describe the relationship between a qualitative dependent variable (that is, one which can take only certain discrete values, such as the presence or absence of a disease) and an independent variable. A common application is in epidemiology for estimating an individual's risk (probability of a disease) as a function of a given risk factor.
  • Logistic regression
    • Wikipedia
      A form of regression analysis that models an individual's odds of disease or some other outcome as a function of a risk factor or intervention. It is widely used for dichotomous outcomes, in particular to carry out adjusted analysis.
  • Log-odds ratio
    • Wikipedia
      The (natural) log of the odds ratio. It is used in statistical calculations and in graphical displays of odds ratios in systematic reviews.
  • Logistic models
    • MeSH
      Statistical models which describe the relationship between a qualitative dependent variable (that is, one which can take only certain discrete values, such as the presence or absence of a disease) and an independent variable. A common application is in epidemiology for estimating an individual's risk (probability of a disease) as a function of a given risk factor.
  • Longitudinal study
    • MeSH - Wikipedia
      An observational study design in which measurements are made over a period of time.
      Studies in which variables relating to an individual or group of individuals are assessed over a period of time.
  • Longitudinal prospective study
    • An observational study design in which the investigators follow subjects for future events.
  • Long-term care
    • MeSH - Wikipedia
      Long-term care encompasses a broad range of help with daily activities that chronically disabled individuals need for a prolonged period of time.
      Care over an extended period, usually for a chronic condition or disability, requiring periodic, intermittent, or continuous care.
  • Long-term outcomes
    • Changes that occur as a result of many interventions. Long-term outcomes are likely to be changes in behavior, conditions (e.g. risk factors), and status (e.g. poverty rates).
  • Loss to follow-up
    • The circumstance that occurs when researchers lose contact with some participants and thus cannot complete planned data collection efforts. A common cause of missing data, especially in long-term studies.
  • Lot quality assurance sampling
    • MeSH
      A sampling methodology using small sample sizes when conducting surveys in small geographical or population-based areas or lots.
  • Low birth weight
    • MeSH
      Low birth weight is defined as a weight of less than 2,500 g (up to and including 2,499 g), irrespective of gestational age.
      An infant having a birth weight of 2,500 gm. (5.5 lb.) or less but infant, very low birth weight is available for infants having a birth weight of 1,500 grams (3.3 lb.) or less.
  • Low-birth-weight newborns
    • The percentage of live births that weigh less than 2,500 g out of the total of live births during the same time period.
      Percentage of liveborn infants that weigh less than 2,500 g, for a given time period.
  • Low birthweight proportion
    • The number of newborn children weighing less than 2,500 grams, as weighted at the time of birth or within the first hours of life, before significant postnatal weight loss has occurred, expressed per 100 live births, for a given year, in a given country, territory, or geographic area.