The distribution of passenger vehicle speeds traveling on a certain freeway in California is nearly normal with a mean of 73.7 miles/hour and a standard deviation of 4.72 miles/hour. The speed limit on this stretch of the freeway is 70 miles/hour. (a) A highway patrol officer is hidden on the side of the freeway. What is the probability that 5 cars pass and none are speeding?
Assume that the speeds of the cars are independent of each other. (Round your answer to four decimal places.)
(b) On average, how many cars would the highway patrol officer expect to watch until the first car that is speeding?
(c) What is the standard deviation of the number of cars he would expect to watch?

a)  0.2347, 0.0007

b) 1.30

c) 0.63

Step-by-step explanation:

Given –  

Mean = 73.4

Sigma = 4.7

Probability that the speed is greater than 70 is  

P (X>70) = P (z> (70-73.4)/4.7) = P (z>-0.72) = 0.7653

a)The probability that a car is not speeding = 1 - 0.7653 = 0.2347

The probability that all 5 cars are not speeding = (0.2347)5 = 0.0007

b)E (X) = 1/p = 1/0.7653 = 1.30  

c)Standard deviation = Sqrt (1-p/p) = (1-0.7653)/0.7653 = 0.63

answear:

a

step-by-step explanation: a

a) one student is chosen from classroom a, then a student is chosen from classroom b.  

step-by-step explanation:

independent events are ones in which the probability of one event does not affect the probability of the second event.

one student is chosen from classroom a; this does not affect the chances of choosing a student from classroom b.   this makes these independent events.

when one card is chosen from a standard deck and then set aside before a second card is chosen, the probability of the second card being chosen changes.   this makes them dependent events.

when one student is chosen from classroom a and then a second student is chosen from classroom a, the probability of choosing the second student changes.   this makes them dependent events.

when a letter is chosen from the alphabet and then a second letter is chosen, the probability of choosing the second letter changes.   this makes them dependent events.