NAG Library Manual, Mark 28.5
```    Program g07cafe

!     G07CAF Example Program Text

!     Mark 28.5 Release. NAG Copyright 2022.

!     .. Use Statements ..
Use nag_library, Only: g07caf, nag_wp
!     .. Implicit None Statement ..
Implicit None
!     .. Parameters ..
Integer, Parameter               :: nin = 5, nout = 6
!     .. Local Scalars ..
Real (Kind=nag_wp)               :: clevel, df, dl, du, prob, t, xmean,  &
xstd, ymean, ystd
Integer                          :: ifail, nx, ny
Character (1)                    :: equal, tail
!     .. Executable Statements ..
Write (nout,*) 'G07CAF Example Program Results'
Write (nout,*)

!     Skip heading in data file

!     Read in the sample sizes, means and standard deviations

!     Display data
Write (nout,*) 'Sample X'
Write (nout,99996) '  Sample size        = ', nx
Write (nout,99995) '  Mean               =', xmean
Write (nout,99995) '  Standard deviation =', xstd
Write (nout,*)
Write (nout,*) 'Sample Y'
Write (nout,99996) '  Sample size        = ', ny
Write (nout,99995) '  Mean               =', ymean
Write (nout,99995) '  Standard deviation =', ystd

d_lp: Do

!       Read in the type of statistic and CI required
If (ifail/=0) Then
Exit d_lp
End If

!       Calculate statistic
ifail = 0
Call g07caf(tail,equal,nx,ny,xmean,ymean,xstd,ystd,clevel,t,df,prob,   &
dl,du,ifail)

!       Display results
Write (nout,*)
If (equal=='E' .Or. equal=='e') Then
Write (nout,*) 'Assuming population variances are equal.'
Else
Write (nout,*) 'No assumptions about population variances.'
End If
Write (nout,*)
Write (nout,99999) 't test statistic         =  ', t
Write (nout,99998) 'Degrees of freedom       = ', df
Write (nout,99997) 'Significance level       =    ', prob
Write (nout,*)
Write (nout,99999) 'Difference in means'
Write (nout,99999) '  Value                  = ', xmean - ymean
Write (nout,99999) '  Lower confidence limit = ', dl
Write (nout,99999) '  Upper confidence limit = ', du
Write (nout,99999) '  Confidence level       = ', clevel
End Do d_lp

99999 Format (1X,A,F10.4)
99998 Format (1X,A,F8.1)
99997 Format (1X,A,F8.4)
99996 Format (1X,A,I5)
99995 Format (1X,A,E11.4)
End Program g07cafe
```