Question

Astronomers treat the number of stars in a given volume of space as a Poisson random variable. The density in the Milky Way Galaxy in the vicinity of our solar system is 1 star per 16 cubic light years. (a) What is the probability of 3 or more stars in 16 cubic light years?(b) How many cubic light years of space must be studied so that the probability of one or more stars exceeds 0.92?

Answer 1

Answer:

a) 0.264

b) 48 cubit light-years

Step-by-step explanation:

For calculating a)  What is the probability of 3 or more stars in 16 cubic light years?

a)

λ= 1 star/16 cubic light-years

t= measure t in units of 16 cubic light years.

E(Y) = λ t = (1/16)(16) = 1 star

P(X>=2) = 1 - P(X<2)

= 1 - [e^-1 + (e^-1)(1)/1!]

= 0.264

b)

P(X≥1) = 1 - P(X=0)

= 1 - e^-μ

0.95 = 1 - e^-μ

e^-μ = 1 - 0.95

e^-μ = 0.05

ln(e^-μ) = ln(0.05)

-μ = -3

μ = 3

Therefore  3 x 16 = 48 cubic light years of space