Items tagged “statistics”
41 results found
The student t-test is an analysis of variance that is found in many radiology studies. To use the test on the data, the data must: be a comparison of only two groups must not be "matched data" (e.g. before and after results for the same group) must be from a normally distributed population ...
ANOVA (ANalysis Of VAriance) is a statistical technique commonly seen in radiology research. ANOVA analyzes are conceptually similar to the student t-test, but involve comparison of multiple groups at once. The alternative to an ANOVA would be multiple head-to-head t-tests, but this would likel...
Case reports are a type of radiology research literature. They belong to the class of descriptive studies. Purpose The purpose of a radiology case report is to describe the patient history, clinical course, and imaging for a notable or unusual case. The case may be intended to aid other practi...
A case series is essentially a collection of case reports around a common theme. It belongs to the class of descriptive studies. Structure A case series typically contains: a short introduction the series of cases patient history, presentation, imaging, and clinical course are described in ...
The likelihood ratios (LR) can be useful to judge the probability of an event. They allow to calculate predictive values independent of disease prevalence: LR+ = sensitivity / (1 - specificity) LR- = (1 - sensitivity) / specificity
Multiple regression analysis
Multiple regression analysis is a commonly used statistical technique in radiology research. It allows the examination of the relationship between multiple variables in a quantifiable manner. This technique is often used where there are multiple explanations (independent variables / co-variates...
Pearson's chi-squared test
The Pearson's chi-squared test is one of the most common statistical tests found in radiology research. It is a type of non-parametric test, used with two categorical variables (not continuous variables). Concept The heart of the chi-squared test is a 2 x 2 contingency table. We usually have ...
The paired t-test is the appropriate method when the researcher takes an experimental group, measures the baseline, subjects the members to an intervention, and then measures the results. Testing in a before-and-after manner like this ("matched data" or "repeated measures") requires a different...
Kappa is a nonparametric test that can be used to measure interobserver agreement on imaging studies. Cohen's kappa compares two observers, or in the case of machine learning can be used to compare a specific algorithm's output versus labels. Fleiss' kappa assesses interobserver agreement betwee...
Selection bias is a type of bias created when the data sampled is not representative of the data of the population or group that a study or model aims to make a prediction about. Selection bias is the result of systematic errors in data selection and collection. Practically-speaking selection bi...
Confusion matrices, a key tool to evaluate machine learning algorithm performance in classification, are a statistical tool. Contingency tables, a type of confusion matrix, are used in the evaluation of many diagnostic exams for sensitivity, specificity, positive and negative predictive values....
Single linear regression
Single linear regression, also known as simple linear regression, in statistics, is a technique that maps a relationship between one independent and one dependent variable into a first-degree polynomial. Linear regression is the simplest example of curve fitting, a type of mathematical problem i...
Retrospective studies are cohort or case-control studies that analyze existing data from before the time point at which the study began. These studies are more susceptible to bias and confounding than prospective studies.
Prospective studies are usually longitudinal or cohort studies, although they can be case control studies, that examine whether an outcome occurs during the time period of the study.
Bayes' theorem, also known as Bayes' rule or Bayes' law, is a theorem in statistics that describes the probability of one event or condition as it relates to another known event or condition. Mathematically, the theory can be expressed as follows: P(A|B) = (P(B|A) x P(A) )/P(B), where given that...
A Bayes' factor is a number that quantifies the relative likelihood of two models or hypotheses to each other if made into a ratio e.g. if two models are equally likely based on the prior evidence ( or there is no prior evidence) then the Bayes factor would be one. Such factors have several use...
The incidence is an epidemiological term for the number of new cases of a condition (e.g. brain tumors or diabetes), in a given population, during a specified time interval. The formulas for incidence can express it as a rate or a proportion, e.g. x new cases / y population count / z time period...
The prevalence is an epidemiological term referring to the proportion that reflects total disease/condition burden in a population at a specific time. There are different kinds of prevalence: point prevalence is the amount of disease at one point in time period prevalence is prevalence over a...
Impact factor is a bibliometric index. It expresses the "impact" of a publication on the reference scientific community. Specifically, it measures the average number of citations of a scientific article by other researchers. The impact factor was developed in 1961 by the Institute for Scientifi...
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Published 03 Nov 2021