In a Task Where the Observer Compares the Weight of a Constant

In a task where the observer compares the weight of a constant comparison stimulus with the weights of a changing stimulus using the method of limits, the interval of uncertainty is operationally defined as

A) the mean of the upper and lower thresholds.
B) the difference between the upper and lower thresholds.
C) the distance between the means of the signal and noise distributions.
D) the mean of the stimulus values corresponding to the last "heavier" response and the first "equal," response.