| Term 
 | Definition 
 
        | EITHER the observer of the measurements does not know OR the subject of the experimental treatment does not know in which group (experimental or control) the subjects have been placed |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | NEITHER the researcher NOR the subjects know who is receiving the experimental or placebo treatment |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | anything that mistakenly influences the conclusions about groups and distorts comparisons. |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | Inappropriate selection of study subjects; often leads to incorrect relationships between risk factor(s) and disease |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | Inappropriate collection of information during the study; often leads to incorrect relationships between risk factor(s) and disease |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | some known or unknown factor is associated with both the risk factor and the outcome; often leads to incorrect relationships between risk factor(s) and outcome (disease) |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | study design in which persons with a disease of interest (cases) are compared with those without the disease (controls); researchers look back to identify possible causes |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | a professional article that describes the diagnostic, preventive, and therapeutic services rendered to a patient with an unusual or complex condition |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | a journal article that describes a series of cases of an unusual or complex condition |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | An experiment designed to test the effect of an agent or procedure on two or more groups |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | group of individuals with similar characteristics |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | study where the same subjects are followed over a period of time to observe the occurrence of a particular event |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | Group that does not receive the independent variable (may receive a placebo or no treatment at all).  An equivalent group used for comparison |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | descriptive study where variable(s) is/are measured at one point or limited period or time |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | Study conducted on a population (i.e. entire city) where independent variable is either added or removed and the outcome is measured |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | An investigation of similar groups of individuals over an extended period of time in order to identify a change or development in that group |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | research design that attempts to approximate the standards of experimentation, but falls short of the control and precision required; random assignment of participants is not possible |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | framework or blueprint for conducting a study |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | A subset of measurements selected from a population of interest.  A part or subset of the population used to gain information about the whole |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | sample consisting of entire population |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | subjects chosen from whatever portion of the population is easiest to reach - access to total is not possible
 - risk of bias
 |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | someone with knowledge of population arbitrarily selects the sample to represent the population - risk of bias
 |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | subjects chosen in such a way that every member of the population has an equal chance of being selected to be in the sample - increases external validity
 - reduces chance of bias
 |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | subjects chosen from subgroups proportionately in the sample with similar characteristics |  | 
        |  | 
        
        | Term 
 | Definition 
 
        | every nth member of population is selected; ānā can represent any number; essentially equivalent to simple random sampling |  | 
        |  |