Final answer:
The mean number of correct answers when guessing on each question is 425.
Step-by-step explanation:
To find the mean number of correct answers when guessing on true or false questions, we can use the formula for the mean of a binomial distribution.
The probability of getting a question correct by guessing is 0.5 (since there are two options: true or false). So the mean number of correct answers is equal to the total number of questions multiplied by the probability of getting a question correct:
Mean number of correct answers = 850 x 0.5 = 425
Therefore, the mean number of correct answers when guessing on each question is 425.