A total of 5498 union members were randomly assigned to receive 1 of 3 different informational letters : 1 without a testimonial ( No Testimonial Group ) , 1 with a testimonial from a person whose shared union affiliation with the recipient was not disclosed ( Unaffiliated Testimonial Group ) , and 1 with a testimonial from a person whose shared union affiliation with the recipient was disclosed ( Affiliated Testimonial Group ) .