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Welch's t-test: Difference between revisions
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</lang>
=={{header|Fortran}}==
Using IMSL function '''TDF'''. With Absoft Pro Fortran, compile with '''af90 %FFLAGS% %LINK_FNL% pvalue.f90'''.
<lang fortran>subroutine ttest_welch(n1, x1, n2, x2, t, df, p)
use tdf_int
implicit none
integer :: n1, n2
double precision :: x1(n1), x2(n2)
double precision :: m1, m2, v1, v2, t, df, p
m1 = sum(x1) / n1
m2 = sum(x2) / n2
v1 = sum((x1 - m1)**2) / (n1 - 1)
v2 = sum((x2 - m2)**2) / (n2 - 1)
t = (m1 - m2) / sqrt(v1 / n1 + v2 / n2)
df = (v1 / n1 + v2 / n2)**2 / &
(v1**2 / (n1**2 * (n1 - 1)) + v2**2 / (n2**2 * (n2 - 1)))
p = 2d0 * tdf(-abs(t), df)
end subroutine
program pvalue
implicit none
double precision :: x(4) = [3d0, 4d0, 1d0, 2.1d0]
double precision :: y(3) = [490.2d0, 340.0d0, 433.9d0]
double precision :: t, df, p
call ttest_welch(4, x, 3, y, t, df, p)
print *, t, df, p
end program</lang>
'''Output'''
<pre> -9.55949772193266 2.00085234885628 1.075156114978449E-002</pre>
=={{header|Go}}==
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