Question

Plz help me with this

Answer 1

Answer: mean = 3.6,  standard deviation = 3

Step-by-step explanation:

$\text{Mean: }\dfrac{90\times 4}{100}=\dfrac{360}{100}=3.6\\\\\\\text{Standard Deviation: }\\\bullet n=100\qquad \rightarrow \text{number of students}\\\bullet p=0.9\qquad \rightarrow \text{probability of success}\\\bullet q=0.1\qquad \rightarrow \text{probability of failure}\\\\SD=\sqrt{n\times p\times q}\\.\quad =\sqrt{(100)(0.9)(0.1)}\\.\quad =\sqrt{9}\\.\quad =3$