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Measure developers use the C-statistic to assess risk-adjusted models, it indicates the ability of the model to discriminate between one event and the other. If a model discriminates randomly, c = 0.5. If the risk factor modeling predicts the outcome well, then discrimination increases. The higher the c-statistic, the better the predictive power of the model.

Calculation Algorithm

A calculation algorithm is an ordered sequence of data element retrieval and aggregation through which numerator and denominator events or continuous variable values are identified by a measure. Also referred to as the performance calculation.

Chi-square test

Chi-square test measures the statistical significance of a difference in proportions. It is a statistical test commonly used to compare observed data with data one would expect to obtain according to a specific hypothesis.
Pelletier, L. R., & Beaudin, C. L. (Eds.). (2012). Q solutions: Essential resources for the healthcare quality professional (3rd ed.). National Association for Healthcare Quality.

Clinical Practice Guidelines

Clinical practice guidelines are systematically developed statements to support practitioner and patient decisions about appropriate health care for specific clinical circumstances.

Clinical Quality Language (CQL)

CQL is a Health Level Seven International® mixed normative/Standard for Trial Use. It is part of the effort to harmonize standards between electronic clinical quality measures and clinical decision support. CQL provides the ability to express logic that is human-readable yet structured enough for processing a query electronically.

Clinical Quality Measure (CQM)

A clinical quality measure is a mechanism used for assessing the degree to which a measured entity competently and safely delivers clinical services appropriate for the patient in an optimal time frame. CQMs are a subset of the broader category of performance measures.

CMS Consensus-Based Entity

The Medicare Improvements for Patients and Providers Act of 2008 requires the U.S. Department of Health and Human Services to contract with a consensus-based entity (CBE) regarding performance measurement. The CMS CBE endorses quality measures through a transparent, consensus-based process incorporating feedback from diverse groups of interested parties to foster health care quality improvement.

Cochran's Q

Cochran's Q test is a statistical test used to determine whether the proportion of "successes" is equal across three or more groups in which the same individuals appear in each group. Zach. (2021, January 26). What is Cochran's Q test? Statology. Retrieved November 27, 2023, from 

Code Language

A code language, also known as programming language, is a set of commands, instructions, and other syntax used to create a software program. A high-level language is what a programmer uses to write code. The programmer compiles the code into a low-level language, which computer hardware recognizes directly. Christensson, P. (2011). Programming language. Retrieved November 1, 2023, from

Code System

A code system is a managed collection of concepts with each concept represented by at least one internally unique code and a human-readable description (e.g., SNOMED CT).

Coefficient of Stability

The coefficient of stability is an index of reliability determined via a test-retest method in which the same test is administered to the same respondents at two different points in time.
APA Dictionary of Psychology. (n.d.). Stability coefficient. Retrieved November 27, 2023, from

Cohen's Kappa

Cohen's kappa, or Cohen's Kappa coefficient, is a quantitative measure of agreement of categorical variables between two raters (inter-rater reliability) or one rater at two time periods (intra-rater reliability). A Cohen's kappa of 0 indicates agreement equivalent to chance. A Cohen's kappa of 1 indicates total agreement.


Collinearity is when two or more variables are exactly correlated, which means the regression coefficients are not uniquely determined. Collinearity hurts the interpretability of the model because the regression coefficients are not unique and have influences from other features. Saslow, E. (2018). Collinearity - What it means, why its bad, and how does it affect other models? Medium. Retrieved November 1, 2023, from

Competing Measures

Competing measures address the same topic and the same population. Use this term when considering harmonization. See also Related Measures.

Composite Measure

A composite measure is a measure containing two or more individual measures, resulting in a single measure with a single score.

Conceptual Framework

A conceptual framework is a theoretical structure of assumptions, principles, and rules holding together the ideas comprising a broad concept.

Concordance Rate

The concordance rate is a statistical measure describing the proportion of pairs of individuals sharing an attribute, given that one already possesses this trait. A pair is considered concordant if they both possess an attribute of interest and discordant if they differ. It is commonly used to estimate the influence of nature and nurture on the development of a particular attribute or disease in an individual.

Skiold-Hanlin, S. (n.d.). Concordance rate | Definition, calculation & interpretation. Retrieved November 27, 2023, from

Confidence Interval

A confidence interval (CI) provides a range of possible values around a sample estimate (a mean, proportion, or ratio) calculated from data. CIs are commonly used when comparing groups and reflect the always-present uncertainty when working with samples of subjects. Rosati, R. J., & Quality, N. a. F. H. (2012). Q Soultions: Information Management. 

Conflict of Interest

A conflict of interest exists when an individual (or entity) has more than one motivation for trying to achieve an objective. In measure development, this situation arises when an individual has opportunities to affect specifications for quality measures impacting an interest with which the individual has a relationship.

Construct Validity

Construct validity is the extent to which the measure actually measures what it claims to measure. Construct validity evidence often involves empirical and theoretical support for the interpretation of the construct.

Continuous Variable (CV)

A continuous variable is a measure score in which each individual value for the measure can fall anywhere along a continuous scale and can be aggregated using a variety of methods such as the calculation of a mean or median (e.g., mean number of minutes between presentation of chest pain to the time of administration of thrombolytics).

Convergent Validity (concurrent validity)

Convergent validity refers to the degree to which multiple measures of a single concept are correlated.

Cost of Care

The cost of care is the total health care spending, including total resource use and unit price, by payer or consumer, for a health care service or group of health care services associated with a specified patient population, time period, and unit of clinical accountability.

Cost/Resource Use Measure

A cost/resource use measure is a measure of health services counts (in terms of units or dollars) applied to a population or event (including diagnoses, procedures, or encounters). A resource use measure counts the frequency of use of defined health system resources. Some may further apply a dollar amount (e.g., allowable charges, paid amounts, or standardized prices) to each unit of resource use.


Covariate is a variable that affects a response variable but is not of interest in the study. Zach. (2020, September 25). What is a Covariate in Statistics? Statology. 


A criterion is an accepted standard, principle, or rule used to make a decision or to inform an evaluator’s judgment.

Criterion Validity

Criterion validity measures how well one measure predicts the outcome for another measure or verifies data elements against some reference criterion determined to be valid (i.e., the gold standard).

Critical Data Element

A critical data element is an element contributing most to the computed measure score, meaning it accounts for identifying the greatest proportion of the target condition, event, or outcome being measured (numerator); the target population (denominator); population excluded (exclusion); and when applicable, risk factors with largest contribution to variability in outcome.

Cronbach's Alpha

Cronbach's alpha is a quantitative measure of internal consistency reliability. Cronbach's alpha ranges between 0 and 1, with higher values indicating more reliability.