Stevens' Power Law

Stevens' Power Law calculator computes a proposed relationship between the magnitude of a physical stimulus and its perceived intensity or strength. Stevens' methods are usually applied in global psychophysics, meaning the stimuli would be discriminated correctly with nearly perfect certainty for any population.

INSTRUCTIONS: Enter the following:

• (k)  Proportionality Constant (based on units used)
• (I) Physical Magnitude of Stimulation
• (a) Exponent given to I (depends on the type of stimulation)

Magnitude of Sensation (Ψ): The calculator computes the subjective magnitude of sensation.

The Math

The formula for Stevens' Power Law is as follows:

            Ψ = k•I^a   

where:

• ψ is the Steven's Law magnitude of sensation.
• k is a proportionality constant that is based on the units used
• I is the physical magnitude of the stimulation
• a is the exponent given to I that depends on the type of stimulation

Ψ is the subjective magnitude of the sensation evoked by the stimulus.  For your convenience, the corresponding table of exponents that Stevens reported is provided in the table.

Source

The Wikipedia page on Stevens' Power Law is located HERE.

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