Problem: Dr. Izmen decided to conduct research multiple nights at the county fair. He decided to observe patrons on both weeknights and weekends, as well as in the afternoon, early evening, and late evening. He had research assistants throughout the fair, at different booths, noting observations about parenting behaviors and romantic relationship behaviors. He was able to collect data on a diverse sample in age, ethnicity, sex, and socioeconomic status. Dr. Izmen's study has: Group of answer choices high external validity. lack of representativeness. observer bias. low external validity.