第五章测试1.
Variables which take on values only at certain points over a given interval are called _______.
A:point variables
B:discrete random variables
C:value variables
D:continuous random variables
答案:B
2.
A variable that can take on values at any point over a given interval is called _______.
A:a discrete random variable
B:a continuous random variable
C:a value variable
D:a point variable
3.
You are offered an investment opportunity. Its outcomes and probabilities are presented in the following table.
X | P(X) |
–$1000 | .40 |
$0 | .20 |
+$1000 | .40 |
The mean of this distribution is _____________.
A:$0 B:$400 C:–$400
D:$200 4.
You are offered an investment opportunity. Its outcomes and probabilities are presented in the following table.
X | P(X) |
–$1000 | .40 |
$0 | .20 |
+$1000 | .40 |
The standard deviation of this distribution is _____________.
A:$894
B:$663
C:$800,000
D:–$400
5.
The long-run average or mean of a Poisson distribution is usually referred to as _______.
A:m
B:a
C:s
D:l
6.
The variance of a Poisson distribution is equal to _______.
A:l2
B:l
C:l/2
D:
7.If X is a binomial random with n = 8 and p = 0.6, what is the probability that X is less than or equal to 2?
A:0.375 B:0.009 C:0.050 D:0.041 8.
If X is a binomial random with n = 8 and p = 0.6, what is the probability that X is greater than 2?
A:0.011 B:0.124
C:0.950
D:0.991
9.
Twenty-five items are sampled. Each of these has the same probability of being defective. The probability that exactly 2 of the 25 are defective could best be found by _______.
A:using the exponential distribution
B:using the Poisson distribution
C:using the normal distribution
D:using the binomial distribution
10.
You are offered an investment opportunity. Its outcomes and probabilities are presented in the following table.
X | P(X) |
–$1000 | .40 |
$0 | .20 |
+$1000 | .40 |
Which of the following statements is true?
A:This distribution is skewed to the right.
B:This is a binomial distribution.
C:This distribution is skewed to the left.
D:This distribution is symmetric.
