Items tagged “statistics”
48 results found
Case
P-values
Published
09 Nov 2021
41% complete
Article
Probability vs odds
The likelihood of an occurrence (called an “event”) can be expressed as a probability or as odds.
Probability (P) tells us how often a particular event occurs on average over the course of many trials. For example, the probability of rolling a 4 with a fair 6-sided die is 1/6. Think of probabil...
Case
Odds and likelihood ratios
Published
02 Dec 2023
25% complete
Diagram
Article
Diagnostic test accuracy
The accuracy of a diagnostic test is defined as how often the test correctly classifies someone as having or not having the disease. The formula for accuracy is:
(true positive + true negative) / (true positive + true negative + false positive + false negative)
or correct results / all results...
Article
Alpha vs beta error
Clinical trials may have incorrect results due to random error or bias. The 2 types of random error are called alpha (α) and beta (β), also known as type I and type II errors respectively. Alpha and beta errors are both conditional probabilities. For Radiologists, it may be helpful to think of α...
Article
Hypothesis testing
Hypothesis testing is a statistical method used to evaluate clinical trial results and consists of four consecutive steps:
specification of the null hypothesis and the alternative hypothesis
data collection
statistics and p-value calculation
rejection or failure to reject the null hypothesis...
Article
Number needed to screen
The number needed to screen (NNS) is the number of patients that need to undergo screening to prevent one death by the disease being screened for1,2. The number is calculated by taking the reciprocal of the absolute risk reduction as follows:
calculate the risk (probability) of death from the d...
Article
Meta-analysis
Meta-analysis (plural: meta-analyzes) is a statistical technique that returns in a single numerical estimate (synthesis) the results of multiple clinical trials relating, for example, to the same pharmacological treatment 1,2. Meta-analyzes of RCTs specifically, are the most robust evidence of e...
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