1
COMM 215- Midterm Practice Exam with Accurate Solutions
1. If P(A) = 0.66, P(B) =0.74 and P(A U B) =0.80, then P(A ∩ B) is:
a) 0.06
b) 0.14
c) 0.60
d) 0.83
2. Let the random variable X follow a normal distribution with a mean of μ = 50 and a standard deviation
of σ = 10 What is the value of k such that P(42<X<k) = 0.76?
a) 69.1
b) 67.8
c) 66.4
d) 64.0
10. Which of the following statements is true?
a) The mean is always less than the median
b) The mean may not be included among the values
c) The sum of the squared deviations from the mean is always zero
d) The standard deviation is always smaller than the variance
14. If A and B are independent events with P(A) = 0.20 and P(B) =0.60, then P(B | A) is:
a) 0.20
b) 0.60
c) 0.40
d) 0.80
15. As product manager of a new brand of toothpaste you want to determine the proportion of households
who are aware of your product. How large of a sample would you need to take in order to ensure that
you are within 5 percent of the population proportion? Assume you want to have 95% reliability.
a) 714
b) 653
c) 687
d) 385
18. If s 2 =225 , s =484 , and Cov(X,Y) = 198, then the correlation coefficient is:
2
x y
a) 0.60
b) 0.70
c) 0.85
d) 0.80
SECTION B: 6 APPLICATION QUESTIONS – (Total of 88 Points)
1. Student scores in a specific test are normally distributed. A random sample of ten scores found the following
results: (20 points)
, 2
93, 71, 62, 76, 81, 63, 88, 59, 84, 73.
COMM 215- Midterm Practice Exam with Accurate Solutions
1. If P(A) = 0.66, P(B) =0.74 and P(A U B) =0.80, then P(A ∩ B) is:
a) 0.06
b) 0.14
c) 0.60
d) 0.83
2. Let the random variable X follow a normal distribution with a mean of μ = 50 and a standard deviation
of σ = 10 What is the value of k such that P(42<X<k) = 0.76?
a) 69.1
b) 67.8
c) 66.4
d) 64.0
10. Which of the following statements is true?
a) The mean is always less than the median
b) The mean may not be included among the values
c) The sum of the squared deviations from the mean is always zero
d) The standard deviation is always smaller than the variance
14. If A and B are independent events with P(A) = 0.20 and P(B) =0.60, then P(B | A) is:
a) 0.20
b) 0.60
c) 0.40
d) 0.80
15. As product manager of a new brand of toothpaste you want to determine the proportion of households
who are aware of your product. How large of a sample would you need to take in order to ensure that
you are within 5 percent of the population proportion? Assume you want to have 95% reliability.
a) 714
b) 653
c) 687
d) 385
18. If s 2 =225 , s =484 , and Cov(X,Y) = 198, then the correlation coefficient is:
2
x y
a) 0.60
b) 0.70
c) 0.85
d) 0.80
SECTION B: 6 APPLICATION QUESTIONS – (Total of 88 Points)
1. Student scores in a specific test are normally distributed. A random sample of ten scores found the following
results: (20 points)
, 2
93, 71, 62, 76, 81, 63, 88, 59, 84, 73.
