3. For each day that Sasha travels to work, the probability that she will experience a delay due to
traffic is 0.2. Each day can be considered independent of the other days.
(a) For the next 21 days that Sasha travels to work, what is the probability that Sasha will
experience a delay due to traffic on at least 3 of the days?
(b) What is the probability that Sasha’s first delay due to traffic will occur after the fifth day of
travel to work?

(c) Consider a random sample of 21 days that Sasha will travel to work. For the proportion of
those days that she will experience a delay due to traffic, is the sampling distribution of the
sample proportion approximately normal? Justify your answer

the answer   is 200

step-by-step explanation:

this is a problem about poisson probabilities.   i don't know if you've

already studied poisson distributions, or if you have a place to look

to read more about the subject.  

here's how you can see a poisson distribution coming.   when there are

a lot of events that may happen at any time (or any place), and when

you're counting how many of them happen at a particular time (or a

particular place), and each event is independent of the others, then

the result is a poisson distribution.   this is roughly true for the

chocolate chips; one chip being in a cookie has only a small effect on

the probability that another chip will be in the cookie.

once you know you have a poisson distribution, you know a lot.   there

is only one parameter to a poisson distribution, so if you know the

mean, you know everything.   the form of the distribution is

  probability of n chips = {[e^(-x)]*(x^n)} / (n! )

1: -2 3/4, -2 1/2, -14, 0, 3, 8 1/3

2: -4, -3, -2 1/2, -2 1/4, 3 1/4,

step-by-step explanation:

your answer is  

a.

5

step-by-step explanation:

30,40,50 is correct answer