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# Conditional Probability & Independence

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Problem #38 review question need help

The key formula on the second page is the formula needed to use to complete number 38. This is supplementary exercise to help me. Solution and explanation.

38. A Morgan Stanley Consumer Research Survey sampled men and women and asked each whether the preferred to drink plain bottled water or a sports drink such as Gatorade or Propel Fitness water (The Atlanta Journal -Constitution, December 28, 2005). Suppose 200 men and 200 women participated in the study, and 280 reported they preferred plain bottled water. Of the group preferring a sports drink, 80 were men and 40 were women.

Let

M = the event the consumer is a man
W = the event the consumer is a woman
B = the event the consumer Preferred plain bottled water
S = the event the consumer Preferred sports drink.

a. What is the probability a person in the study preferred plain bottled water?
b. What is the probability a person in the study preferred a sports drink?
c. What are the conditional probabilities P (M|S) and P (W|S)?
d. What are the joint probabilities P (M&#8745;S) and P (W&#8745;S)?
e. Given a consumer is a man, what is the probability he will prefer a sports drink?
f. Given a consumer is a woman, what is the probability she will prefer a sports drink?
g. Is preference for a sports drink independent of whether the consumer is a man or woman? Explain using probability information.