The example above shows that the rate of decay is not linear with time. Examination of the curve produced by plotting the data indicates the change is logarithmic. The function can be linearized in this way:
where No is the starting sample and N is the sample remaining at time t. The value k is the rate constant for the decay and is the negative slope of the straight line when the equation is written in this form.
Realistically, decay data is not this pretty. There is a good deal of scatter generally since the decay process is somewhat random. All the more reason to attempt to linearize the function before using it to make predictions.