stats_cdf_t

(PECL stats >= 1.0.0)

stats_cdf_t — Calculates any one parameter of the t-distribution given values for the others.

说明

float stats_cdf_t ( float $par1 , float $par2 , int $which )

Returns the cumulative distribution function, its inverse, or one of its parameters, of the t-distribution. The kind of the return value and parameters (par1 and par2) are determined by which.

The following table lists the return value and parameters by which. CDF, x, and nu denotes cumurative distribution function, the value of the random variable, and the degrees of freedom of the t-distribution, respectively.

Return value and parameters
which Return value par1 par2
1 CDF x nu
2 x CDF nu
3 nu x CDF

参数

par1

The first parameter

par2

The second parameter

which

The flag to determine what to be calculated

返回值

Returns CDF, x, or nu, determined by which.

User Contributed Notes

Anonymous 13-Apr-2012 04:30
Input  and return values of stats_cdf_t depends on the $which-parameter:
<?php
function get_t_p($t, $df){
  return stats_cdf_t($t, $df, 1);
}
function get_t_t($p, $df){
  return stats_cdf_t($p, $df, 2);
}
function get_t_df($p, $t){
  return stats_cdf_t($p, $t, 3);
}
?>
Brian 14-Oct-2010 11:14
In order to match the output of this function with Excel's TDIST function, you must take 1 - the value.  For example, for a two-tailed T-distribution for x=4 and degrees of freedom=2, the formula would be:

(1 - stats_cdf_t(4, 2, 1)) * 2

For a single tail, do not include the multiply by 2 portion.