Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
149 Cards in this Set
- Front
- Back
|
data summarized by groups, for example summary outcome data for treatment and control groups |
aggregate data |
|
|
The loss of participants during the course of a study |
attrition |
|
|
systematic differences between comparison groups in withdrawals or exclusions of participants from the results of a study; for example, patients may drop out of a study because of intervention side effects, and excluding them from the analysis could result in an overestimate of the effectiveness of the intervention |
attrition bias |
|
|
a systematic error or deviation in results or inferences from the truth |
bias |
|
|
bias that arises from systematic differences in the groups that are compared |
selection bias |
|
|
bias that arises from the care that is provided , exposure to other factors apart from the intervention of interest |
performance bias |
|
|
bias that arises due to how outcomes are assessed |
detection bias |
|
|
a statistical distribution with known properties describing the number of occurrences of an event in a series of observations |
binomial distribution |
|
|
the process of preventing those involved in a trial from knowing to which group a particular participant belongs |
blinding |
|
|
a study reporting observations on a series of individuals, usually all receiving the same intervention, with no control group |
case series |
|
|
a study reporting observations on a single individual |
case study, anecdote, case history, single case report |
|
|
a study that compares people with a specific disease or outcome of interest to people from the same population without that disease or outcome, and which seeks to find associations between the outcome and prior exposure to particular risk factors; particularly useful where the outcome is rare and past exposure can be reliably measured |
case control study |
|
|
data that are classified into two or more non-overlapping categories |
categorical data |
|
|
a trial in which clusters of individuals rather than individuals themselves are randomized into different arms |
cluster randomized trial |
|
|
the application of additional diagnostic or therapeutic procedures to people receiving a particular program of treatment |
co-intervention |
|
|
an observational study in which a defined group of people is followed over time; the outcomes of people in subsets of this study are compared, to examine people who were exposed, not exposed, or exposed at different levels to a particular intervention |
cohort study |
|
|
a type of cohort study that identifies subjects from past records and follows them from the time of the records to the present |
retrospective |
|
|
a measure of the uncertainty around the main finding of a statistical analysis |
confidence interval |
|
|
a comparison between two treatment groups that will give a biased estimate of the effect of treatment due to the study design; in order to not have this characteristic, the two groups must be treated identically apart from the randomized treatment |
confounded comparison |
|
|
a factor that is associated with both an intervention/exposure and the outcome of interest; a major concern in non-randomized studies |
confounder |
|
|
the inadvertent application of the intervention being evaluated in a study to people in the control group; or inadvertent failure to apply the intervention to people assigned to the intervention group |
contamination |
|
|
data with a potentially infinite number of possible values within a given range (i.e. height, weight, blood pressure) |
continuous variable |
|
|
a group of individuals being studied because they are easily accessible in some way; could make them particularly unrepresentative as they are not a random sample of the whole population. |
convenience sample |
|
|
linear association between two variables, measured by a coefficient |
correlation |
|
|
a type of clinical trial comparing two or more interventions in which the participants, upon completion of the course of one treatment, are switched to another |
cross-over trial |
|
|
a study measuring the distribution of some characteristics in a population at a particular point in time |
cross-sectional study |
|
|
refers to the number of independent contributions to the sampling distribution |
degrees of freedom |
|
|
the outcome or response that results from changes to an independent variable; plotted on the vertical axis on a graph |
dependent variable |
|
|
a study that describes characteristics of a sample of individuals; investigators do not actively intervene to test a hypothesis, but merely describe the health status or characteristics of a sample from a defined population |
descriptive study |
|
|
a number that describes how much larger of a sample is needed in designs such as cluster randomized trials to achieve the same precision as a simple random sample; the ratio of the true variance of a statistic to the variance of the statistic for a simple random sample with the same number of cases |
design effect |
|
|
systematic difference between comparison groups in how outcomes are ascertained, diagnosed, or verified |
detection bias |
|
|
data that can take one of two possible values, such as dead/alive, present/not present |
dichotomous/binary data |
|
|
the collection of values of a variable in the population or the sample |
distribution |
|
|
a response to a drug which may be related to the amount received |
dose dependent |
|
|
the relationship between the quantity of treatment given and its effect on outcome |
dose response relationship |
|
|
results that are based on observation rather than reasoning along |
empirical |
|
|
the study of health of populations and communities, not just particular individuals |
epidemiology |
|
|
a state of uncertainty where a person believes it is equally likely that either of two treatment options is better |
equipoise |
|
|
a trial designed to determine whether the response to two or more treatments differs by an amount that is clinically unimportant. This is usually demonstrated by showing that the true treatment difference is likely to lie between a lower and an upper level of clinically acceptable differences |
equivalence trial |
|
|
a study in which the investigators actively intervene to test a hypothesis |
experimental study |
|
|
a trial that aims to test a treatment policy in an ideal situation where patients receive the full course of therapy as prescribed, and use of other treatments may be controlled or restricted |
explanatory trial |
|
|
the extent to which results provide a correct basis for generalizations to other circumstances |
external validity |
|
|
a trial design used to assess the individual contribution of treatments given in combination, as well as any interactive effect they may have; usually carried out in circumstances where no interaction is likely |
factorial design |
|
|
a conclusion that a person does not have the disease or condition being tested, when they actually do |
false negative |
|
|
a conclusion that a person does have the disease or condition being tested, when they actually do not |
false positive |
|
|
a graphical display of some measure of study precision plotted against effect size that can be used to investigate whether there is a link between study size and treatment affect |
funnel plot |
|
|
the probability of an event occurring given that it hasn't occurred up to the current point in time |
hazard rate |
|
|
a measure of effect produced by a survival analysis; represents the increased risk with which one group is likely to experience the outcome of interest |
hazard ratio |
|
|
describes the variation in or diversity of participants, interventions, and measurement of outcomes across a set of studies; the presence of variability among studies beyond the amount expected due solely to chance |
heterogeneity |
|
|
a control person or group for whom data were collected earlier than for the group being studied |
historical control |
|
|
participants, interventions, and measurement of outcomes are similar across a set of studies; effect estimates of a set of studies where they do not vary more than would be expected by change |
homogeneous |
|
|
the number of new occurrences of something in a population over a particular period of time (the number of cases of disease in a country over one year) |
incidence |
|
|
a description of two events, where knowing the outcome or value of one does not inform us about the outcome or value of the other |
independent |
|
|
an exposure, risk factor, or other characteristic that is hypothesized to influence the dependent variable (measured variable) |
independent variable |
|
|
a strategy for analyzing data from an RCT; all participants are included in the arm to which they were allocated, whether or not they received or completed the intervention given to that arm. Assists in preventing bias caused by loss of participants, which may disrupt the baseline equivalence established by randomization and which may reflect non-adherence to the protocol. |
intention to treat analysis |
|
|
a degree of stability exhibited when a measurement is repeated under identical conditions by different raters |
interrater reliability |
|
|
the degree to which the results obtained by a measurement procedure can be replicated |
reliability |
|
|
the situation in which the effect of one independent variable on the outcome is affected by the value of a second independent variable in a trial; examines whether the treatment effect varies across sub-groups of participants |
interaction |
|
|
analysis comparing intervention groups at any time before formal completion of the trial |
interim analysis |
|
|
the extent to which the design and conduct of a study are likely to have prevented bias; more rigorously designed trials are more likely to yield results that are closest to the truth |
internal validity |
|
|
a research design that collects observations at multiple time points before and after an intervention; design attempts to detect whether the intervention has had an effect significantly greater than the underlying trent |
interrupted time series |
|
|
the degree of stability exhibited when a measurement is repeated under identical conditions at different times by the same rater |
intra-rater reliability |
|
|
a form of analysis that models an individual;s odds of disease or some other outcome as a function of a risk factor or intervention |
logistic regression |
|
|
a scatter plot of the risk in the experimental group against the risk in the control group |
L'Abbe plot |
|
|
choosing one or more controls with particular same attributes for each case |
matching |
|
|
the use of statistical techniques in a systematic review to integrate the results of included studies |
meta-analysis |
|
|
a technique used to explore the relationship between study characteristics and study results in a systematic review |
meta-regression |
|
|
a method of allocation used to provide comparison groups that are closely similar for several variables |
minimization |
|
|
a statistical model in which the combined effect of several factors is the product of the effects produced each in the absence of the others |
multiplicative model |
|
|
measuring the impact of more than one variable at a time while analyzing a set of data |
multivariate analysis |
|
|
a measure of the usefulness of a screening/diagnostic test; the proportion of those with a negative test result that do not have the disease, the probability that a negative test result is correct |
negative predictive value |
|
|
a statistical distribution with known properties commonly used as the basis of models to analyze continuous data; assumptions include that the data are distributed around a mean value, and the shape of the distribution can be described using the mean and standard deviation |
normal distribution |
|
|
the statistical hypothesis that one variable has no association with another variable or set of variables (that the factor of interest has no impact on outcome) |
null hypothesis |
|
|
a study in which the investigators do not seek to intervene, and simply observe the course of events; changes or difference sin one characteristic are studied in relation to changes or differences in other characteristics without action by the investigator; greater risk of selection bias than in experimental studies |
observation study |
|
|
a way of expressing the chance of an event, calculated by dividing the number of individuals in a sample who experienced the event by the number for whom it did not occur |
odds |
|
|
a hypothesis test in which the values for which we can reject the null hypothesis are located entirely in one place in the probability distribution; testing whether one treatment is better than another rather than testing whether one treatment is either better or worse than another |
one-tailed test |
|
|
data that are classified into more than two categories that have a natural order |
ordinal data |
|
|
a component of a participant's clinical and functional status after an intervention has been applied, that is used to assess the effectiveness of an intervention |
outcome |
|
|
the probability (ranging from 0 to 1) that the results observed in a study could have occurred by chance if in reality the null hypothesis were true (that they are not associated); assesses the overall statistical significance of the difference between the intervention groups |
P value |
|
|
a study in which participants or groups of participants are matched based on prognostic factors; one member of each group is then allocated to the experimental and the other to the control group |
paired design |
|
|
a trial that compares two groups of people concurrently, one of which receives the intervention of interest and one of which is a control group |
parallel group trial |
|
|
an analysis of the subset of participants in an RCT who complied with the protocol sufficiently to ensure that their data would be likely to exhibit the effect of treatment |
per protocol analysis |
|
|
systematic differences between intervention groups in care provided apart from the intervention being evaluated; if participants know they are in the control group, they may be more likely to use other forms of care; if care providers are aware of the group a participant is in, they may act differently |
performance bias |
|
|
a difference in the measured outcomes from one treatment period to another; could be caused by all patients in a trial naturally healing over time |
period effect |
|
|
the average number of years that each participant is followed up for, multiplied by the number of participants |
person-years |
|
|
a measure of usefulness of a screening/diagnostic test; the proportion of those with a positive test result who have the disease, and can be interpreted as the probability that a positive test result is correct |
positive predictive value |
|
|
the probability of rejecting the null hypothesis when a specific alternative hypothesis is true; one minus the probability of a type II error; the probability that a trial will detect as statistically significant an intervention effect of a specified size; with this value at .80-if a trial was repeated 100 times, it would find a statistically significant treatment effect in 80 of them. |
statistical power |
|
|
a trial that aims to test a treatment policy in a "real life" situation, when many people may not receive all of the treatment, and may use other treatments as well; opposite of an explanatory trial which is done under ideal conditions |
pragmatic trial |
|
|
a measure of the likelihood of random errors in the results of a study; the higher this number is, the less the random error. Narrower confidence intervals cause this measure to be higher as well. |
precision |
|
|
the proportion of a population having a particular condition or characteristic |
prevalence |
|
|
a study in which people are identified according to current risk status or exposure, and followed forwards through time to observe outcome. RCTs always fall into this category, as well as some cohort studies.
|
prospective study |
|
|
a value assigned to represent the validity of a study either for a specific criterion, or overall; can use letters or numbers |
quality score |
|
|
error due to chance; confidence intervals and p values allow for entrance of this type of error |
random error |
|
|
a bias arising from mistakes in recollecting events, both because of failures of memory and looking at things with hindsight and possibly changed views |
recall bias |
|
|
a statistical modeling technique used to estimate or predict the influence of one or more independent variables on a dependent variable |
regression analysis |
|
|
a bias caused by only a subset of all the relevant data being available
|
reporting bias |
|
|
a study in which the outcomes have occurred to the participants before the study commenced; usually case control studies, sometimes cohort studies, but never RCTs |
retrospective studies |
|
|
the proportion of participants experiencing the event of interest |
risk |
|
|
an aspect of a person's condition, lifestyle, or environment that affects the probability of occurrence of a disease |
risk factor |
|
|
a period before randomization when participants are monitored but they receive no treatment; data used to screen out ineligible or non-compliant participants, ensure they are in stable condition, and provide baseline observations |
run-in period |
|
|
an outcome used to evaluate additional effects of the intervention deemed a priori as being less important than the primary outcomes |
secondary outcomes |
|
|
systematic differences between comparison groups in prognosis or responsiveness to treatment; randomization with concealment of this allocation to groups can decrease this type of bias. Affects external validity. |
selection bias |
|
|
a measure of the test's ability to correctly detect people with the disease; the proportion of diseased cases that are correctly identified by the test (# with disease with positive test/# with disease) |
sensitivity |
|
|
a randomized trial in which the data are analyzed after each participant's results become available, and the trial continues until a clear benefit is seen in favor of one of the comparison groups, or it is unlikely that any difference will emerge |
sequential trial |
|
|
a measure of the test's ability to correctly identify people who do not have the disease; the proportion of people without the target disease who are correctly identified by the test; (# without disease who have a negative test/# without disease) |
specificity |
|
|
a measure of the spread or dispersion of a set of observations, calculated as the average difference from the mean value in a sample |
standard deviation |
|
|
a measure of the variation in the sample statistic over all possible samples of the same size; decreases as the sample size increases |
standard error |
|
|
the difference between two estimated means divided by an estimate of the standard deviation; is used to combine results from studies using different ways of measuring the same concept |
standardized mean difference/d index |
|
|
a result that is unlikely to have happened by chance; threshold for this judgment is that the results, or more extreme results, would occur by chance with a probability of less than .05 if the null hypothesis were true |
statistically significant |
|
|
the process by which groups are separated into mutually exclusive sub-groups of the population that share a characteristic; then can compare these different sub-groups to see if effects of treatment differ |
stratification |
|
|
a method used to ensure that equal numbers of participants with a characteristic thought to affect prognosis or response to the intervention will be allocated to each comparison group |
stratified randomization |
|
|
outcome measures that are not of direct practical importance but are believed to reflect outcomes that are important; often physiological or biochemical markers that can be quickly and easily measured, and that are taken as being predictive of important clinical outcomes |
surrogate endpoints |
|
|
a statistical distribution describing the distribution of the means of samples taken from a population with unknown variance |
t distribution |
|
|
a statistical hypothesis test that is used to compare continuous data in two groups |
t test |
|
|
a hypothesis test in which the values for which we can reject the null hypothesis are located entirely in both tails of the probability distribution; testing whether one treatment is better OR worse than another |
two tailed test |
|
|
a conclusion that a treatment works, when it actually does not work; risk of this error is alpha. Describes the chance of rejecting the null hypothesis when it is in fact true
|
type I error/false positive |
|
|
a conclusion that there is no evidence that a treatment works, when it actually does work; risk is beta. describes the chance of NOT rejecting the null hypothesis when it is in fact false. Risk of this type of error decreases as the number of participants in a study increases |
type II error/false negative |
|
|
a comparison between two treatment groups that will give an unbiased estimate of the effect of treatment due to the study design; treatment groups must be treated identically apart from the randomized treatment |
unconfounded comparison |
|
|
statistical analyses that are not specific in the trial protocol, and are generally suggested by the data |
unplanned/post hoc analyses |
|
|
the degree to which a result of a measurement or study is likely to be true and free of bias (systematic errors) |
validity |
|
|
a measure of the variation shown by a set of observations, equal to the square of the standard deviation; defined as the sum of the squares of deviations from the mean, divided by the number of observations, minus 1 |
variance |
|
|
the stage after the first treatment is withdrawn and before the second treatment is started; aims to allow time for any active effects of the first treatment to wear off before the new one is started |
wash out period |
|
|
the proportion of patients in the experimental group who are observed to experience the outcome of interest |
experimental event rate |
|
|
the chance that a given test result would be expected in a patient with the target disorder compared with the chance that this same result would be expected in a patient without the disorder |
likelihood ratio |
|
|
a systematic review that uses quantitative methods to synthesize and summarize the results |
meta-analysis |
|
|
patient undergoes pairs of treatment periods organized so that one period involves use of the treatment and other involves use of an alternate or placebo therapy; blinded if possible. outcomes monitored and treatment periods are replication until clinician and patient are convinced that the treatments are definitely different or not different |
N of 1 trials |
|
|
the proportional reduction in rates of bad outcomes between experimental and control participants in a trial |
relative risk reduction |
|
|
the absolute arithmetic difference in rates of bad outcomes between experimental and control participants in a trial |
absolute risk reduction |
|
|
the proportional increase in rates of good outcomes between experimental and control patients in a trial |
relative benefit increase |
|
|
the absolute arithmetic difference in rates of good outcomes between experimental and control patients in a trial |
absolute benefit increase |
|
|
the proportional increase in rates of bad outcomes between experimental and control patients in a trial |
relative risk increase |
|
|
the absolute arithmetic difference in rates of bad outcomes between experimental and control patients in a trial |
absolute risk increase |
|
|
the extent to which a test developed from a theory measure a certain idea as defined by a theory |
construct validity |
|
|
a non-statistical type of validity that involves the systematic examination of the test content to determine whether it covers a representative sample of the behavior domain to be measured; evaluates test items against the test specifications/construct it should measure |
content validity |
|
|
an estimate of whether a test appears to measure a certain criterion; does not guarantee that the test actually measures the phenomena in that domain; may have a high validity, but when the test does not appear to be measuring what it actually is, it has a low value of this type of validity |
face validity |
|
|
involves the correlation between the test and a variable taken as representative of the construct; compares the test with other measures or outcomes already held to be valid |
criterion validity |
|
|
the degree to which test results correlate with other measures of the same construct that are measured at the same time |
concurrent validity |
|
|
the degree to which the test can correlate with other measures of the same construct that are measured at some time in the future |
predictive validity |
|
|
an estimate of the degree to which conclusions about causal relationships can be made, based on the measures used, the research setting, and the whole research design; RCTs increase this type of validity |
internal validity |
|
|
the extent to which the results of a study can be held true for other cases, for example to different people, places, or times; whether findings can be validly generalized. Is the study sample representative of the general population along relevant dimensions? |
external validity |
|
|
the extent to which research results can be applied to real-life situations outside of research settings; to what degree experimental findings mirror what can be observed in the real world |
ecological validity |
|
|
the degree to which conclusions about the relationship among variables based on the data are correct or reasonable; involves ensuring the use of adequate sampling procedures, appropriate statistical tests, and reliable measurement procedures |
statistical conclusion validity |
|
|
the process of deciding whether the numerical results quantifying hypothesized relationships between variables are acceptable as descriptions of the data |
regression validation |
|
|
number that indicates the proportion of the variance in the dependent variable that is predictable from the independent variables; provides a meesure of how well observed outcomes are replicated by the model, based on the proportion of total variation of outcomes explained by the model |
R2, coefficient of determination |
|
|
standardized measure of dispersion of a probability or frequency distribution; often expressed as a percentage (ratio of standard deviation to the mean) |
coefficient of variation/relative standard deviation |
|
|
a measure of the strength and direction of the linear relationship between two variables that is defined as the covariance of the variables divided by the product of their standard deviations |
Pearson product moment correlation coefficient (r) |
|
|
establishes that, for most commonly studied scenarios, when independent random variables are added, their sum tends toward a normal distribution (bell curve) even if the original variables themselves are not normally distributed |
central limit theorem |
|
|
the number of patients who need to be treated to prevent one bad outcome or produce one good outcome; the number of patients a clinician would have to treat with the experimental treatment compared to the control treatment to achieve one additional patient with a favorable outcome |
numbers needed to treat (NNT) |
|
|
a variable whose influence distorts the true relationship between a potential risk factor and the clinical outcome of interest |
confounding variable |
