For a television program about astrology, investigators went into the street and found twenty volunteers born under the sign of Gemini who were willing to be interviewed on the program and to take a personality test  The test confirmed the investigators' personal impressions that each of the volunteers was more sociable and extroverted than people are on average
This modest investigation thus supports the claim that one' s astrological birth sign influences one' s personality
People who are not sociable and extroverted are not likely to agree to participate in such an investigation.