In a study of 352 girl with a particular disease, the subjects were injected with vitamin to determine if the vitamins have an effect on the disease. Does the given description correspond to an observational study or an experiment?

Television viewing reached a new high when the global information and measurement company reported a mean daily viewing time of 8.35 hours per household. use a normal probability distribution with a standard deviation of 2.5 hours to answer the following questions about daily television viewing per household. a. what is the probability that a household views television between 4 and 10 hours a day? (to 4 decimals) b. how many hours of television viewing must a household have in order to be in the top 7% of all television viewing household? (to 2 decimals) c. what is the probability that a household views television more than 4 hours a day? (to 4 decimals)