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Standard Deviation/Probability...Help!?
Based on past data, 28% of the people who listen to a sales presentation for an investment product will ultimately purchase the product. Twenty people who have listened to the presentation are surveyed afterwards. Round to 3 decimal places.
a. How many people do you expect will purchase the product after the presentation?
b. What is the standard deviation?
c. What is the probability that exactly 4 people will purchase the product?
d. What is the probability that at most 7 people will purchase the product?
e. What is the probability that 5 or more people will purchase the product?
Please help me figure these out. Thanks!
1 Answer
- M3Lv 78 years agoFavorite Answer
a. E[X] = np = 20*.28 = 5.6 <------
b. sd = √(npq) = √(20*0.28*0.72) = 2.008 <-----
c. P(X=4) = 20c4 *0.28^4 *0.72^16 = 0.155 <------
computing similarly,
d. P(0 <= X <= 7) = 1 - P(X > 7) = 0.829 <------
e. P(5 <= X <= 20) = 1 - P(X <5) = 0.698 <------