What type of testing was performed on this formula to validate efficacy?

We conducted consumer perception testing of a panel of 57 total users in a range of natural and color-treated hair shades including silver, blonde, redheads, and brunettes. Because SEM (electron microscope imaging) often does not detect the nuances in removing brassiness and yellowing from certain hair shades (especially in highlights and balayage), we chose a relatively large consumer perception panel, as the users generally know their “fresh” and “optimal” hair tone.