During a season change, a pathologist observed that out of 10,000 people tested for viral fever, 1000 people were tested positive. Then the standard deviation for the distribution of positive reports is ______
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 30
Each person tested is either positive or not, so the number of positive reports follows a binomial distribution with
\( \displaystyle n=10000,\quad p=\frac{1000}{10000}=0.1,\quad q=0.9 \)
\( \displaystyle \sigma=\sqrt{npq} \)
\( \displaystyle =\sqrt{10000\times0.1\times0.9} \)
\( \displaystyle =\sqrt{900} \)
\( \displaystyle =30 \)