Chapter 8: Problem 12
Explain the difference between \(\sigma\) and \(\sigma_{\bar{x}}\) and between \(\mu\) and \(\mu_{\bar{x}}\)
Chapter 8: Problem 12
Explain the difference between \(\sigma\) and \(\sigma_{\bar{x}}\) and between \(\mu\) and \(\mu_{\bar{x}}\)
All the tools & learning materials you need for study success - in one app.
Get started for freeThe time that a randomly selected individual waits for an elevator in an office building has a uniform distribution over the interval from 0 to \(1 \mathrm{~min}\). It can be shown that for this distribution \(\mu=0.5\) and \(\sigma=0.289\). a. Let \(\bar{x}\) be the sample average waiting time for a random sample of 16 individuals. What are the mean and standard deviation of the sampling distribution of \(\bar{x}\) ? b. Answer Part (a) for a random sample of 50 individuals. In this case, sketch a picture of a good approximation to the actual \(\bar{x}\) distribution.
The article "Should Pregnant Women Move? Linking Risks for Birth Defects with Proximity to Toxic Waste Sites" (Chance [1992]: 40-45) reported that in a large study carried out in the state of New York, approximately \(30 \%\) of the study subjects lived within 1 mi of a hazardous waste site. Let \(\pi\) denote the proportion of all New York residents who live within 1 mi of such a site, and suppose that \(\pi=.3\). a. Would \(p\) based on a random sample of only 10 residents have approximately a normal distribution? Explain why or why not. b. What are the mean value and standard deviation of \(p\) based on a random sample of size \(400 ?\) c. When \(n=400\), what is \(P(.25 \leq p \leq .35)\) ? d. Is the probability calculated in Part (c) larger or smaller than would be the case if \(n=500 ?\) Answer without actually calculating this probability.
An airplane with room for 100 passengers has a total baggage limit of 6000 lb. Suppose that the total weight of the baggage checked by an individual passenger is a random variable \(x\) with a mean value of \(50 \mathrm{lb}\) and a standard deviation of \(20 \mathrm{lb}\). If 100 passengers will board a flight, what is the approximate probability that the total weight of their baggage will exceed the limit? (Hint: With \(n=100\), the total weight exceeds the limit when the average weight \(\bar{x}\) exceeds \(6000 / 100\).)
A manufacturing process is designed to produce bolts with a 0.5-in. diameter. Once each day, a random sample of 36 bolts is selected and the diameters recorded. If the resulting sample mean is less than \(0.49\) in. or greater than \(0.51\) in., the process is shut down for adjustment. The standard deviation for diameter is \(0.02\) in. What is the probability that the manufacturing line will be shut down unnecessarily? (Hint: Find the probability of observing an \(\bar{x}\) in the shutdown range when the true process mean really is \(0.5\) in.)
A certain chromosome defect occurs in only 1 out of 200 adult Caucasian males. A random sample of \(n=100\) adult Caucasian males is to be obtained. a. What is the mean value of the sample proportion \(p\), and what is the standard deviation of the sample proportion? b. Does \(p\) have approximately a normal distribution in this case? Explain. c. What is the smallest value of \(n\) for which the sampling distribution of \(p\) is approximately normal?
What do you think about this solution?
We value your feedback to improve our textbook solutions.