Question

At Central High School, 85% of all senior girls attended and 65% of all senior boys attended the Spring Dance. Of all attendees, 20% won a prize. A. Assuming that the number of senior girls at Central High School is about equal to the number of senior boys, estimate the probability that a randomly selected senior won a prize at the dance. Explain. Enter your answer. B. Construct Arguments If you knew whether the selected student was a boy or a girl, would your estimate change

Answer 1

a) 30%

b) the estimate wouldnt change as far as the probabilities is been maintained. thre can only be a shift in the gender probability depending on whether there are more number of boys or girls.

Explanation:

a) Prob( all senior girl attended) = 85%

Prob ( all senior boy attended) = 65%

Prob( won a price) = 20%

Prob( a senior girl attends and win a price) = 85% x 20%

= 17%

Prob ( a senior boy attends and win a price) = 65% x 20%

= 13%

Prob( a senior won a price) = 17% + 13%

= 30%

b) The estimate wouldnt change as far as the probabilities is been maintained. thre can only be a shift in the gender probability depending on whether there are more number of boys or girls.

Answer 2

a) 0.30 (30%)

b) Boy: 0.13 (13%) , Girl : 0.17 (17%)

Explanation:

Given:-

- The probability of senior girls attend spring dance, P(GA) = 0.85

- The probability of senior boys attend spring dance, P(BA) = 0.65

- The probability that an attendee wins a prize, P(W) = 0.20

Find:-

Estimate the probability that a randomly selected senior won a prize at the dance.

Construct Arguments If you knew whether the selected student was a boy or a girl, would your estimate change

Solution:-

- First realize that the probability for any senior student to attends the spring dance and winning a prize are independent events.

- So for independent events, the probability that a "girl or a boy" attends the spring dance and wins a prize can be determined:

P ( GA & W ) = P(GA)*P(W) = 0.85*0.20 = 0.17 (17%)

P ( BA & W ) = P(BA)*P(W) = 0.65*0.20 = 0.13 (13%)

P ( (BA & W) U (GA & W) ) = P ( BA & W ) + P ( GA & W )

= 0.17 + 0.13

Answer = 0.3 (30%)

- So the estimate probability that a randomly selected senior won a prize at the dance is 0.3 or 30% of all attendee.

- If the randomly selected senior was a girl would be the proportion of people who won the prize.

P ( GA & W ) = 0.17 (17%)

- Similarly, If the randomly selected senior was a boy would be the proportion of people who won the prize.

P ( BA & W ) = 0.13 (13%)