Monday, 28 October 2013

Bartlett's Test Calculator for Equality of Variance

There are statistical tests that involve three or more groups or datasets, and that require the variances of all the groups to be the same, such as the ANOVA test. Bartlett's test can be used to test for equality (more precisely, homogeneity) of variances between groups, and requires that all the data are Gaussian distributed in order to yield a reliable result. For more details on how to carry out Bartlett's test, have a look at the following post.

Simply click on the link directly below to add text boxes. Each text box stores a single group/dataset and needs to be filled in with comma separated numbers. Alternatively, you can choose two file entry methods:-

  1. Select multiple single column CSV files to populate the text boxes by repeatedly pressing the Choose File button - there must be one distinct (and differently named) file for each text box i.e. one file per group. Each file can have a different number of samples.
  2. Select a single multi-column CSV file by pressing the Choose File button once, where the number of columns equals the number of groups - all groups need to have the same number of samples.

There is a graph at the bottom which will display scatter plots for all the groups, once the calculate button is pressed.

Please click to add a dataset group - need at least three

Results pending...

Scatter plot of all the groups
Sample values
Group number

Weibull Distribution CDF and Quantile Calculator

An implementation of the Weibull Distribution CDF and Quantile function Calculator occurs below. The Weibull distribution function (for scale $\lambda>0$ and shape $k>0$) is:-

$\Large \frac{k}{\lambda}(\frac{x}{\lambda})^{k-1}exp(-(\frac{x}{\lambda})^k)$  

where the random variable is $0 < x < \infty$. The scale and shape fields have to be filled in, as well as two out of the three fields which are labelled Lower Limit, Upper Limit and Probability. The lower limit field needs to contain a real number greater or the string -inf (for minus infinity). The upper limit field needs to contain either a number greater than or equal to 0 or the string inf (for plus infinity). The probability field must contain a number only.


Lower limit:
Upper limit:

Plot of distribution ($f(x)$) values against $x$ values