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The precise reader should note that it is not correct to refer to a confidence interval as giving the probability of the true parameter value being in a given range. Such a statement is not possible in classical statistics. What the confidence interval actually shows is the probability that a new observation would give a certain parameter value, assuming that the best-fit value obtained for the current observation is the true value of the parameter

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The FTOOLS distribution includes in the directory callib/src/gen the subroutines rdpha1.f and wtpha1.f, which can be used in programs reading and writing FITS-format spectral files

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The FTOOLS distribution includes in the directory callib/src/gen the subroutines rdebd1.f, rdrmf1.f, wtebd1.f, wtrmf1.f, which can be used in programs reading and writing FITS format response files

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The FTOOLS distribution includes in the directory callib/src/gen the subroutines rdarf1.f and wtarf1.f, which can be used in programs reading and writing FITS format auxiliary response files

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If this fails ask your local XSPEC manager to fix the file $XANADU/lib/xcoms/hard.pco

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However, in XSPEC v8.60 there will be a command that will estimate this using Monte Carlo methods

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PGPLOT is the name of a Graphics Subroutine Library written by T. J. Pearson at the California Institute of Technology.

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This will be available in v8.60