New expressions and some more precise values for Student´s t-factor

This paper gives a 6-figure table of Student´s t-factors for confidence levels corresponding to the ± ¿, ± 2¿ and ± 3¿ limits of a normal distribution. These values have not hitherto been well tabulated, but they are frequently needed when expressing the random uncertainties of measurements on radio frequency and microwave components. Some closed expressions for the integral required in the problem, which are believed to be original, are derived by a little known elementary method that has wider applications.