# probability and statistics

Suppose every student in your class got a score of 85% on an exam. What are the mean and standard deviation of those exam scores without doing any calculations?

I want to say the mean is 100 and the standard deviation is 1 but I don't know why. If all students scored 85% that would be 100% of them so that's how I got 100 but I don't understand how to reach the standard deviation.

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1. Ummmh, if everybody got an 85, wouldn't the average be 85 ??? , so mean = 85
and since nobody "deviated" from that score, wouldn't the standard deviation be zero ????

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posted by Reiny
2. Suppose the scores of students on an exam are normally distributed with a mean of 507 and a standard deviation of 97. According to the empirical rule, what percentage of students scored between 410 and 604 on the exam?

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