![]() The MedCalc ROC module includes comparison of up to 6 ROC curves. MedCalc is the most user-friendly software for Receiver Operating Characteristic curve (ROC curves) analysis. MedCalc is a complete statistical program for Windows designed to closely match the requirements of biomedical researchers. (Version 22.Free Download MedCalc 22.007 Multilingual Portable Free Download | 43.9 Mb Kirkwood BR, Sterne JAC (2003) Essential medical statistics, 2 nd ed.Altman DG (1991) Practical statistics for medical research. ![]() Note that in MedCalc P-values are always two-sided (or two-tailed). When the P-value is less than 0.05 (P<0.05), the conclusion is that the two means are significantly different. The P-value is the area of the t distribution with n 1 + n 2 − 2 degrees of freedom, that falls outside ± t (see Values of the t distribution table). The significance level, or P-value, is calculated using the t-test, with the value t calculated as: The standard error se of the difference between the two means is calculated as: Where s 1 and s 2 are the standard deviations of the two samples with sample sizes n 1 and n 2. The program first calculates the pooled standard deviation s: Sample size: the number of observations in the sample.Standard deviation: the observed standard deviation.The null hypothesis is the hypothesis that the difference is 0. The P-value is the probability of obtaining the observed difference between the samples if the null hypothesis were true. A significance value (P-value) and 95% Confidence Interval (CI) of the difference is reported. This procedure calculates the difference between the observed means in two independent samples.
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