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71 Cards in this Set
- Front
- Back
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Absolute risk increase (ARI)
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the increase in risk with a new therapy compared with the risk without the new therapy
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Absolute risk reduction (ARR)
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the reduction in risk with a new therapy compared with the risk without the new therapy; it is the absolute value of the difference between the experimental event rate and the control event rate (EER-CER).
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Addition rule
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the rule which states the probability that two or more mutually exclusive events all occur is the sum of the probabilities of each individual event
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Adjusted rate
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a rate adjusted so that it is independent of the distribution of a possible confounding variable.
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Alpha value
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the level of alpha selected in a hypothesis test
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Alternative hypothesis
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the opposite of the null hypothesis. It is the conclusion when the null hypothesis is rejected
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Analysis of covariance (ANCOVA)
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a special type of analysis of variance or regression used to control for the effect of a possible confounding factor.
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Analysis of residuals
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in regression, an analysis of the difference between Y and Y’ to evaluate assumptions and provide guidance on how well the equation fits the data.
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Analysis of variance (ANOVA)
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a statistical procedure that determines whether any differences exist among two or more groups of subjects on one or more factors. The F test is used in ANOVA
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Backward elimination
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a method to select variables in multiple regression that enters all variables into the regression equations and then eliminates the variable that adds the least to the prediction, followed by the other variables one at a time that decrease the multiple R by the least amount until all statistically significant variable are removed from the equation.
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Bayes’ theorem
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a formula for calculating the conditional probability of one event, P (A/B) from the conditional probability of the other event, P (B/A)
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Bias
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the error related to the ways the targeted and sampled populations differ; also called measurement error, it threatens the validity of a study
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Binary observation
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the probability distribution that describes the number of successes X observed in n independent trials, each with the same probability of occurrence.
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Biometrics
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the study of measurement and statistical analysis in medicine and biology.
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Biostatistics
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the application of research study design and statistical analysis to applications in medicine and biology
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Blind study
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an experimental study in which subjects do not know the treatment they are receiving
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Block design
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in analysis of variance, a design in which subjects within each block (or stratum) are assigned to a different treatment
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Bonferroni t
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a method for comparing means in analysis of variance; aka the Dunn multiple-comparison procedure
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Bootstrap
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a method for estimating standard errors or confidence intervals in which a small sample of observations is randomly selected form the original sample, estimates are calculated, and the sample is returned to the original sample. This process continues many times to produce a distribution upon which to base the estimates
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Canonical correlation analysis
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an advanced method for examining the relationships between two sets of interval or numerical measurements made on the same set of subjects.
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Case-control
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an observational study that begins with patient cases who have the outcome or disease being investigated and control subjects who do not have the disease or outcome. It then looks backward to identify possible precursors or risk factors.
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Case-series study
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a simple descriptive account of interesting or intriguing characteristics observed in a group of subjects
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Categorical observation
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a variable who values are categories (an example is type of anemia). Also called a nominal scale
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Cell
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a category of counts or value in a contingency table
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Censored observation
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an observation whose value is unknown, generally because the subject has not been in the study long enough for the outcome of interest, such as death, to occur.
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Central limit theorem
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it states that the distribution of means is approximately normal if the sample size is large enough (n is greater than or equal to 30), regardless of the underlying distribution of the original measurements.
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Chance agreement
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a measure of the proportion of times two or more raters agree in their measurement or assessment of a phenomenon
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Chi-square (X2) distribution
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the distribution used to analyze counts in frequency tables.
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Chi-square (X2) test
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used to test the null hypothesis that proportions are equal or, equivalently, that factors or characteristics are independent or not associated
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Classes or class limits
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the subdivisions of a numerical characteristic (or the widths of the classes) when it is displayed in a frequency table or graph (an example is ages by decades)
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Classification and regression tree (CART) analysis
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a multivariate method used to detect significant relationships among variables which are then used to develop predictive models for classifying future subjects.
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Closed question
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a question on an interview in which a specific set of response options are provided.
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Cluster analysis
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an advanced method that determines a classification or taxonomy from multiple measures of a set of objects or subjects.
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Cluster random sample
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a two-stage sampling process in which the population is divided into clusters, a random sample of clusters is chosen, and then random samples of subjects within the clusters are selected
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Coefficient of determination (r2)
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the square of the correlation coefficient. It is interpreted as the amount of variance in one variable that is accounted for by knowing the second variable.
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Coefficient of variation (CV)
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the standard deviation divided by the mean, generally multiplied by 100. It is used to obtain a measure of relative variation.
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Cohort
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a group of subjects who remain together in the same study over time.
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Cohort study
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an observational study that begins with a set of subjects who have a risk factor and a second set of subjects who do not have the risk factor. Both sets are followed prospectively through time to learn how many in each set develop the outcome or consequences of interest.
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Combination
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a formula in probability that is gives the number of ways a specific number of items can be selected from the total number of items in the entire population or sample
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Complementary event
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an event opposite to the event being investigated
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Concurrent controls
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control subjects assigned to a placebo or control condition during the same period that an experimental treatment or procedure is being evaluated.
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Conditional probability
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the probability of an event given that another event has occurred, denoted P(A/B).
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Confidence bands
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lines on each side of a regression line or curve that have a given probability of containing the line or curve in the population
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Confidence coefficient
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the term in the formula for a confidence interval that determines probability level associated with the interval, such as 90%, 95%, and 99%.
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Confidence interval (CI)
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the interval computed from sample data that has a given probability that the unknown parameter, such as the mean or proportion, is contained within the interval. The ones above are common confidence intervals
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Confidence limits
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the limits of a confidence interval. These limits are computed from sample data and have a given probability that the unknown parameter is located between them.
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Confounded
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a term used to describe a study or observation that has one or more nuisance variables present that may lead to incorrect interpretations.
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Confounding variable
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a variable more likely to be present in one group of subjects than another that is related to the outcome of interest and thus potentially confuses or confounds the results.
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Conservative
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a term used to describe a test if it reduces the chances of a type I error.
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Construct validity
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a demo that the measurement of a characteristic is related to similar measures of the same characteristic and not related to measures of other characteristics.
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Content validity
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a measure of the degree to which the items on a test or measurement scale are representative of the characteristic being measured.
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Contingency table
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a table used to display counts or frequencies for two or more nominal or quantitative variables.
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Continuity correction
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an adaptation to a test statistic when a continuous probability distribution is used to estimate a discrete probability distribution
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Continuous scale
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used to measure a numerical characteristic with values that occur on a continuum (i.e.- age)
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Control event rate (CER)
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the number of subjects in the control group who develop the outcome being studied.
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Control subjects
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in a clinical trial, subjects assigned to the placebo or control condition; in a case-control study, subjects without the disease or outcome.
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Controlled for
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term used to describe a confounding variable that is taken into consideration in the design or the analysis of the study.
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Controlled trial
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subjects are assigned to a control condition as well as to an experimental condition
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Corrected chi square test
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a test for a 2 x 2 table that uses Yates’ correction, making it more conservative.
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Correlation coefficient (r)
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a measure of the linear relationship between two numerical measurements made on the same set of subjects. It ranges from -1 to +1, with 0 indicating no relationship. Aka Pearson product moment.
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Covariate
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a potentially confounding variable controlled for in analysis of covariance
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Cox proportional hazard model
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a regression method used when the outcome is censored. The regression coefficients are interpreted as adjusted relative risk or odds ratios.
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Criterion validity
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an indication of how well a test or scale predicts another related characteristic, ideally a “gold standard”.
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Criterion variable
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the outcome (or dependent variable) that is predicted in a regression problem.
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Critical ratio
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the term for the z score used in tests
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Critical region
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the region or set of values in which a test statistic must occur for the null hypothesis to be rejected.
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Critical value
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the value that a test statistic must exceed (in an absolute value sense) for the null hypothesis to be rejected.
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Crossover study
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a clinical trial in which each group of subjects receives two or more treatments, but in different sequences.
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Cross-sectional study
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an observational study that estimates a characteristic or set of characteristics in a set of subjects at one point in time; a “snapshot” of a characteristic or condition of interest; aka survey or poll.
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Cross-validation
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a procedure for applying the results of an analysis from on sample of subjects to a new sample of subjects to evaluate how well they generalize. It is frequently used in regression.
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Crude rate
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a rate for the entire population that is not specific or adjusted for any given subset of the population
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