Problem 1CQ Determine whether the random variable x is discrete or continuous. Explain your reasoning. (a) Let x represent the number of lightning strikes that occur in Wyoming during the month of June. (b) Let x represent the amount of fuel (in gallons) used by a jet during takeoff. (c) Let x represent the total number of die rolls required for an individual to roll a five.
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Textbook Solutions for Elementary Statistics: Picturing the World
Question
Problem 3CQ
Forty-four percent of U.S. adults believe the U.S. system of justice is fair to most Americans. You randomly select nine U.S. adults. Find the probability that the number of U.S. adults who believe the U.S. system of justice is fair to most Americans is (a) exactly three, (b) at most four, and (c) more than seven.
Solution
Solution :
Step 1 of 3:
From the given information we know that we need to know the probability of a certain number with the characteristic in a finite sample.
Hence the corresponding distribution is the binomial distribution.
Here 44% of U.S. adults .
p = 44%
p =
p = 0.44 and
q = 1-p
q = 1-0.44
q = 0.56
Let n denotes 9 U.S. adults.
The binomial distribution formula is
P(X=k) =
P(X=k) =
Our goal is:
We need to find the probability
a). P(X=3).
b). P(X4).
c). P(X>7).
a). Now we have to find P(X=3).
P(X=3) =
P(X=3) = 0.2206
Therefore, P(X=3) is 0.2206.
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