Thursday, May 30, 2013

Kappa test

Calculate Cohen's kappa statistics for agreement and its confidence intervals followed by testing null-hypothesis that the extent of agreement is same as random, kappa statistic equals zero.

Tuesday, May 14, 2013

LM fitting


A data set has values yi, each of which has an associated modelled value fi (also sometimes referred to as ลทi). Here, the values yi are called the observed values and the modelled values fi are sometimes called the predicted values.
The "variability" of the data set is measured through different sums of squares:
SS_\text{tot}=\sum_i (y_i-\bar{y})^2, the total sum of squares (proportional to the sample variance);
SS_\text{reg}=\sum_i (f_i -\bar{y})^2, the regression sum of squares, also called the explained sum of squares.
SS_\text{err}=\sum_i (y_i - f_i)^2\,, the sum of squares of residuals, also called the residual sum of squares.
In the above \bar{y} is the mean of the observed data:
\bar{y}=\frac{1}{n}\sum_{i=1}^n y_i
where n is the number of observations.
The notations SS_{R} and SS_{E} should be avoided, since in some texts their meaning is reversed to Residual sum of squares and Explained sum of squares, respectively.
The most general definition of the coefficient of determination is
R^2 \equiv 1 - {SS_{\rm err}\over SS_{\rm tot}}.\,

Wednesday, May 1, 2013

Mitochondrial DNA

Mitochondrial DNA (mtDNA or mDNA[2]) is the DNA located in organelles called mitochondria, structures withineukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate (ATP).