Question 44280
Hello!
You calculated the mean number of deaths correctly.

Regarding the standard deviation, notice that the number of deaths follows a binomial distribution, with parameters n = 100 (the total number of patients) and p = 0.7 (the probability of a "success", in this case, that the patient dies, which is 70%). The variance of variable that follows a binomial distribution is given by:

{{{n*p*(1-p)}}}

Pluging the appropiate parameters,

{{{100*0.7*(1-0.7) = 21}}}

Finally, since the standard deviation is the square root of the variance, the we get that the std dev of the number of deaths is:

{{{sqrt(21) = 4.5825}}}


I hope this helps!
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