(ch 3 3.5) An instructor who taught two sections of engineering statistics last

Question

(ch 3 3.5)

An instructor who taught two sections of engineering statistics last term, the first with 25 students and the second with 40, decided to assign a term project. After all projects had been turned in, the instructor randomly ordered them before grading. Consider the first 15 graded projects.

(a) What is the probability that exactly 10 of these are from the second section? (Round your answer to four decimal places.)
0.2172??

(b) What is the probability that at least 10 of these are from the second section? (Round your answer to four decimal places.)
0.4517??

(c) What is the probability that at least 10 of these are from the same section? (Round your answer to four decimal places.)
0.4771??

(d) What are the mean value and standard deviation of the number among these 15 that are from the second section? (Round your mean to the nearest whole number and your standard deviation to three decimal places.)

(e) What are the mean value and standard deviation of the number of projects not among these first 15 that are from the second section? (Round your mean to the nearest whole number and your standard deviation to three decimal places.)

mean ____ projects standard deviation ____ projects

Explanation / Answer

first section has 25 students

second section has 40 students

proabbility of selecting from each section

p1 = 25/65 = 0.384

p2 = 40/65 = 0.615

the probability that exactly 10 of these are from the second section

P(X=10)=(25C5)(40C10)/65C15

= 0.217

b) p(X>=10)

= [(25C5)(40C10)+(25C4)(40C11)+(25C3)(40C12)+.../60C15

= 0.44055

c) answer from above (b) + [(25C10)(40C5)+(25C11)(40C4)+(25C12)(40...
= 0.44055 + 0.01260

= 0.45315

_________________________________

please post d and e seperately since multiple answers cannot be done.

d)

e) same as above

no of students from 1st no of students from 2nd prob 15 0 1.57626E-08 14 1 8.59777E-07 13 2 1.95599E-05 12 3 0.000247759 11 4 0.001964376 10 5 0.010371903 9 6 0.037814229 8 7 0.097236589 7 8 0.178267079 6 9 0.233519449 5 10 0.217173088 4 11 0.141021485 3 12 0.061963986 2 13 0.017407943 1 14 0.002797705 0 15 0.000193974 mean 0.0625 stdev 0.084066838

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