| Statistics
True or False
T F 1. P(X > x ) + P(X < x) + P(X = x) = 1.
T F 2. If P(X > x) = 0.34 and P(X = x) = 0.10, then P(X £ x) = 0.56.
T F 3. In a probability histogram, the area of each rectangle equals the probability that the random variable will take on the value shown below it.
T F 4. A random variable can take on three values. If the first two in the sequence each have a probability of 0.2, the area of rectangle in the probability histogram for the third value will be twice the size of each of the other two rectangles.
T F 5. The only way to ensure complete independence of events when sampling is to sample from a finite population without replacement or from an infinite population with replacement.
T F 6. If the population is large compared to the size of the sample, then the random variable formed by the number of successes in the sample can be assumed to be binomial.
T F 7. Suppose that 40% of a population have blue eyes. The number of people with blue eyes in a sample of 600 has a binomial distribution. The mean of the distribution is 240, and the standard deviation is 12.
T F 8. A light bulb manufacturer claims that 80% of all the bulbs produced will last at least 2000 hours of continuous burning. If a random sample of 200 bulbs is taken from the assembly plant, we can expect 40 to fail before 2000 hours.
T F 9. The normal probability curve is bell shaped and symmetric, irrespective of the value of the mean or the standard deviation.
T F 10. If two normal distributions have the same standard deviation, their means must also be equal.
T F 11. Point estimates are calculated from sample data and are used to estimate population parameters.
T F 12. Because population parameter values are usually known, point estimates are seldom used to measure them.
T F 13. The mean and the median are possible point estimators, but the mode is not.
T F 14. Ideally, a point estimator should yield a value that closely approximates the population parameter.
T F 15. If the upper bound of a confidence interval is added to the lower bound, the sum is the sample mean.
T F 16. The wider the confidence level for the population mean, the greater the precision of the estimate.
T F 17. If a small sample size is coupled with an unknown standard deviation, the normal distribution should not be used to establish a confidence interval for the population mean, even if the population is normally distributed.
T F 18. If the population is not normally distributed but the standard deviation is known, large sample sizes allow us to use the normal distribution to establish a confidence interval for the population mean.
T F 19. By increasing the confidence level, the probability that the interval actually contains the population parameter decreases, and precision is sacrificed.
T F 20. The variability of the t distribution depends on the size of the sample.
Complete the following exercises from the Lind text 12th ed. Worth 10 points each.
Chapter 6, #13
13. An American Society of Investors survey found 30 percent of individual investors have used a discount broker. In a random sample of nine individuals, what is the probability:
a. Exactly two of the sampled individuals have used a discount broker?
b. Exactly four of them have used a discount broker?
c. None of them have used a discount broker?
Chapter 7, #12
12. A normal population has a mean of 12.2 and a standard deviation of 2.5.
a. Compute the z value associated with 14.3.
b. What proportion of the population is between 12.2 and 14.3?
c. What proportion of the population is less than 10.0?
Chapter 9, #12
12. Use Appendix F to locate the value of t under the following conditions.
a. The sample size is 12 and the level of confidence is 95 percent.
b. The sample size is 20 and the level of confidence is 90 percent.
c. The sample size is 8 and the level of confidence is 99 percent.
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Linear Mode
