OBSERVATION: It was not possible to determine conclusively because:

  1. The brightness of the selfies varied since the distance for photographing and the lighting source was not defined beforehand – in other words, the protocol for examination was not standardized and the light sources were not calibrated.
  2. The tooth shades varied greatly amongst the participants at the commencement of the experiment – statistical considerations are required
  3. The new toothpaste appeared to demonstrate some effect on some of the study participants, but not on others– statistical considerations are required
  4. Some of the participants appeared to have less surface staining when they had used their regular toothpaste -– statistical considerations are required

What is at play is the phenomenon termed natural fluctuations, and its statistical counterpart is:
natural variation.

Even though the study design and the idea to detect differences in the photographs was good, a scientific method is usually necessary in order to address assumptions made before the conduct of a study, as was the situation here.