PLEASE NOTE: We are currently in the process of updating this chapter and we appreciate your patience whilst this is being completed. Validity Validity is the extent to which an instrument, such as a survey or test, measures what it is intended to measure (also known as internal validity). This is important if the results of a study are to be meaningful and relevant to the wider population. There are four main types of validity:
Reliability Reliability is the overall consistency of a measure. A highly reliable measure produces similar results under similar conditions so, all things being equal, repeated testing should produce similar results. Reliability is also known as reproducibility or repeatability. There are different means for testing the reliability of an instrument:
Internal consistency can be measured using Cronbach’s alpha (a) – a statistic derived from pairwise correlations between items that should produce similar results. Ranging from minus infinity to one, a Cronbach’s alpha of one indicates perfect internal consistency, and a negative value suggests that there is greater within-subject variability than there is between subjects. Cronbach’s alpha values above 0.7 are generally deemed acceptable. Inter-rater reliability can be measured using the Cohen’s kappa (k) statistic. Kappa indicates how well two sets of (categorical) measurements compare. It is more robust than simple percentage agreement as it accounts for the possibility that a repeated measure agrees by chance. Kappa values range from -1 to 1, where values ≤0 indicate no agreement other than that which would be expected by chance, and 1 is perfect agreement. Values above 0.6 are generally deemed to represent moderate agreement. Limitations of Cohen’s kappa are that it can underestimate agreement for rare outcomes, and that it requires the two raters to be independent. Generalisability Generalisability is the extent to which the findings of a study can be applicable to other settings. It is also known as external validity. Generalisability requires internal validity as well as a judgement on whether the findings of a study are applicable to a particular group. In making such a judgement, you can consider factors such as the characteristics of the participants (including the demographic and clinical characteristics, as affected by the source population, response rate, inclusion criteria, etc.), the setting of the study, and the interventions or exposures studied. Threats to external validity, that may result in an incorrect generalisation, include restrictions within the original study (eligibility criteria), and pre-test/post-test effects (where cause-effect relationships within a study are only found when pre-tests or post-tests are also carried out). © Saran Shantikumar 2018 What term describes a measure of how tightly clustered a group of scores from a data set is around the average?A standard deviation (or σ) is a measure of how dispersed the data is in relation to the mean. Low standard deviation means data are clustered around the mean, and high standard deviation indicates data are more spread out.
What does the reliability of a test refer to quizlet?Terms in this set (6)
Reliability refers to how consistent a study or measuring device is. A measurement is said to be reliable or consistent if the measurement can produce similar results if used again in similar circumstances. Refers to the extent to which a measure is consistent within itself.
What is the outcome variable in an analysis called?The outcome variable is also called the response or dependent variable, and the risk factors and confounders are called the predictors, or explanatory or independent variables. In regression analysis, the dependent variable is denoted "Y" and the independent variables are denoted by "X".
What is an experimental design for assessing age related changes in which data are obtained simultaneously from people of differing ages?Cross-sectional research designs are used to examine behavior in participants of different ages who are tested at the same point in time.
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