StudentA
StudentA (t, DegFree)
This function is deprecated. New code should use the more accurate StatsStudentCDF.
The StudentA function returns the area from -t to t under the Student's T distribution having DegFree degrees of freedom. That is, it returns the probability that a random sample from Student's T is between -t and t.
Note that this is the bi-tail result. That is, it gives the area from -t to t, rather than the cumulative area from -∞ to t. It is this latter number that is commonly tabulated -- StudentA returns the probability 1-α where the area from -∞ to t is the probability 1-α/2.
StudentA tests whether a normally-distributed statistic is significantly different from a certain value. You could use it to test whether an intercept from a line fit is significantly different from zero:
Make/O/N=20 Data=0.5*x+2+gnoise(1) // line with Gaussian noise
Display Data
CurveFit line Data /D
Print "Prob = ", StudentA(W_coef[0]/W_sigma[0], V_npnts-2)
Because the noise is random, the results will differ slightly each time this is tried. When we did it, the result was:
Prob = 0.999898
which indicates that the intercept of the line fit was different from zero with 99.99 per cent probability.