Number Generator - Student-t Distribution
t distribution is used commonly for small sample size -usually a sample
size less than 30. A t distribution shares some common
characteristics with the standard normal distribution. Both
distributions are symmetrical, both range in value from negative
infinity to positive infinity, and both have a mean of zero and
standard derivation of one. However, a t distribution has a
greater dispersion than the standard normal distribution.
The following example shows input and output from 3 simulations.
Each has the degree of freedom of 5,10, and 30 respectively. All
three simulations have 10,000 iterations and alpha of 5% (for 1 tail
output shows the estimate of skewness, mean, stand deviation, maximum
value, minimum value, lower confidence interval, and upper confidence
interval from each of the 3 simulations. As the degree of freedom
(sample size - 1) decreases from simulation 1 to simulation 3, the
standard deviation approaches to 1. The mean remains close to
zero through all 3 simulations.
The following three
charts show as degree of freedom increases, the distribution approaches
* Complete program (with open source
codes) available in Package Set 2 and the Combo Package.