Twenty-five percent of all automobiles undergoing an emissions inspection at a certain inspection station fail the inspection.

Twenty-five percent of all automobiles undergoing an emissions inspection at a certain inspection station fail the inspection. 

(d) What is the probability that among 25 randomly selected cars, the number that pass is within 1 standard deviation of the mean value? 

I think this is a trick question.....

The number that are within 1 standard deviation of the mean in a normal distribution, which I think is assumed here, is always  68%

"Twenty-five percent of all automobiles undergoing an emissions inspection at a certain inspection station fail the inspection. 

(d) What is the probability that among 25 randomly selected cars, the number that pass is within 1 standard deviation of the mean value?"

I've assumed a binomial distribution.  i.e. each car either passes or fails.

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