A developmental psychologist interested in the development of colour perception presented 4 one month-old infants with a pair of colour forms. One form had two colours and the other had one. If the infants preferred to look at the form with two colours above chance level (50%), they can perceive colours. The mean percentage of times the infants preferred the two-colour form was 51 (sample standard deviaiton of 4). What is t_obt?