Apparatus for assessing the accuracy of a target stimulation intensity level used in transcutaneous electrical nerve stimulation to a user, the apparatus comprising: a calculation unit for calculating a set of expected values of the target stimulation intensity level for a desired sensation based on a profile of the user； a stimulation unit for electrically stimulating at least one nerve of the user at one or more stimulation levels； a discovery unit for enabling the user to indicate a target stimulation intensity level at which the electrical stimulation to the user evokes the desired sensation from the user； and an assessment unit to determine the accuracy of the indicated target stimulation intensity level based on the expected set of values of the target stimulation intensity level for the desired sensation.
