Forty of the staff of 85 teachers at a local intermediate school are certified in Cardio-Pulmonary Resuscitation (CPR). In 180 days of school, what would be the expected mean, variance and standard deviation?

Answer and Step-by-step explanation:

The computation is shown below;

Here we use the binomial distribution

p = 40 ÷ 85 = 0.47

q = 1 -0.47 = 0.53

n = 180

Now  

mean

= np

= 180 × 0.47

= 84.6

The Variance is

= npq

= 180 ×  0.47 × 0.53

= 44.84

And,  Standard deviation

= √npq

= √44.84

= 6.69

We simply applied the above formula so that the correct value could come

And, the same is to be considered  

inverse operation of addition