Answers to CRE questions in March 2019 Newsletter

1. X and Y are discrete random variables. The probability that X = 3 is 0.20 and the probability that Y = 4 is 0.30. The probability of observing that X = 3 and Y = 4 concurrently is closest to:

a. 0.06

b. 0.

c. 0.50

**d. Cannot answer with the information provided.**

2. The probabilities that three students will earn an A on an exam are 0.20, 0.25, and 0.30, respectively. If each student’s performance is independent of that of the other two students, the probability that all three students will earn an A is closest to:

**a. 0.0150**

b. 0.0075

c. 0.0010

d. 0.7500

3. The following table summarizes the availability of trucks with air bags and bucket seats at a dealership.

What is the probability of randomly selecting a truck with air bags and bucket seats?

**a. 0.34 **

b. 0.57

c. 0.28

d. 0.16

4. The lower limit of a normal distribution is:

a. negative one

b. zero

c. one

**d. negative infinity**

5. Approximately 50 percent of all observations for a normally distributed random variable fall in the interval:

a. μ ± 2σ

**b. μ ± 0.67σ **

c. μ ± σ

d. μ ± 3σ

6. A depot receives an average of two engines per day to repair. The probability that they will receive 20 engines in 8 days is:

a. 3.66%

b. 16.56%

c. 6.40%

**d. 5.59%**

7. The approximate 99% confidence interval for the population mean based on a sample of 60 returns with a mean of 7% and a sample standard deviation of 25% is closest to:

a. 1.546% to 13.454%

b. 0.546% to 13.454%

**c. -1.59% to 15.589% **

d. 1.584% to 14.584%

8. What is the computed value of the test statistic that follows an F-distribution when sample variances are equal and the level of significance is 0.10?

a. 0.90

b. 0.05

**c. 1.00 **

d. 0.10

9 A survey is taken to determine whether the average starting salaries of Reliability engineers is equal to or greater than $59,000 per year. What is the test statistic given a sample of 135 new Reliability engineers with a mean starting salary of $64,000 and a standard deviation of $5,500?

**a. -0.91 **

b. -10.56

c. 10.56

d. 0.91

10. You have collected monthly returns to depot and want to test the null hypothesis that the standard deviation exceeds the advertised standard deviation of 3.5%. The most appropriate test statistic is based on

**a. chi-square test **

b. t-test

c. F-test

d. z-test

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