Answer:
A
Step-by-step explanation:
when x = 0
Let
be the random variable for the number of marks a given student receives on the exam.
10% of students obtain more than 75 marks, so

where
follows a standard normal distribution. The critical value for an upper-tail probability of 10% is

where
denotes the CDF of
, and
denotes the inverse CDF. We have

Similarly, because 20% of students obtain less than 40 marks, we have

so that

Then
are such that


and we find

Answer:
x = -3
Step-by-step explanation:
simplify
3(x - 4) = -21
3x - 12 = -21
3x = = -9
x = -3
Let X be the number of lightning strikes in a year at the top of particular mountain.
X follows Poisson distribution with mean μ = 3.8
We have to find here the probability that in randomly selected year the number of lightning strikes is 0
The Poisson probability is given by,
P(X=k) = 
Here we have X=0, mean =3.8
Hence probability that X=0 is given by
P(X=0) = 
P(X=0) = 
P(X=0) = 0.0224
The probability that in a randomly selected year, the number of lightning strikes is 0 is 0.0224