A simple naked eye observational exercise is outlined that teaches non-major astronomy students basic observational and critical thinking skills but does not require complex equipment or extensive knowledge of the night sky. Students measure the relationship between stellar scintillation and the altitude of a set of stars. Successful observations provide a correlation that can reveal the fundamental cause of stellar scintillation. Altitude is measured using an outstretched fist (approximately 9 degrees]), while stellar scintillation is measured using a 4-point subjective scale. Seven classes (300 students) have been evaluated and survey results of 72 students suggest the exercise is effective in teaching the intended population. Teaching techniques are outlined that may remediate misconceptions or challenge more advanced classes. (Contains 1 table.)