" A contractor has recently purchased a new bulldozer. On previous jobs, 15 out of a total of 50 bulldozers have broken down before the end of the job.(adsbygoogle = window.adsbygoogle || []).push({});

What is the mean and standard deviation of the probability distribution describing the probability of failure of a bulldozer?

Note: assume a normal approximation is applicable."

Mean of the probablity distribution seems obvious (0.3), but how does one find the standard deviation??

Thanks for any help that can be offered.

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# Help on normal distribution question please

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