Next Contents Previous


In many experiments, the functional relation between two or more variables describing a physical process, y = f(x1, x2, ...), is investigated by measuring the value of y for various of x1, x2, . . .It is then desired to find the parameters of a theoretical curve which best describe these points. For example, to determine the lifetime of a certain radioactive source, measurements of the count rates, N1, N2, . . ., Nn, at various times, t1, t2, . . . , t1, could be made and the data fitted to the expression

Equation 69 (69)

Since the count rate is subject to statistical fluctuations, the values Ni will have uncertainties sigmai = sqrtNi and will not all lie along a smooth curve. What then is the best curve or equivalently, the best values for tau and N0 and how do we determine them? The method most useful for this is the method of least squares.