Chapter 8: Q74E (page 500)
Given \({v_1}\,and\,{v_2}\) find the following probabilities:
- \({v_1} = 2,\,{v_2} = 30,\,p\left( {F \ge 5.39} \right)\)
Short Answer
- The probability is 0.01.
Chapter 8: Q74E (page 500)
Given \({v_1}\,and\,{v_2}\) find the following probabilities:
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Get started for freeProduct failure behavior. An article in Hotwire (December 2002) discussed the length of time till the failure of a product produced at Hewlett Packard. At the end of the product’s lifetime, the time till failure is modeled using an exponential distribution with a mean of 500 thousand hours. In reliability jargon, this is known as the “wear-out” distribution for the product. During its normal (useful) life, assume the product’s time till failure is uniformly distributed over the range of 100 thousand to 1 million hours.
a. At the end of the product’s lifetime, find the probability that the product fails before 700 thousand hours.
b. During its normal (useful) life, find the probability that the product fails before 700 thousand hours.
c. Show that the probability of the product failing before 830 thousand hours is approximately the same for both the normal (useful) life distribution and the wear-out distribution.
Drug content assessment. Refer to Exercise 8.16 (p. 467)and the Analytical Chemistry (Dec. 15, 2009) study in which scientists used high-performance liquid chromatography to determine the amount of drug in a tablet. Recall that 25 tablets were produced at each of two different, independent sites. The researchers want to determine if the two sites produced drug concentrations with different variances. A Minitab printout of the analysis follows. Locate the test statistic and p-value on the printout. Use these values and to conduct the appropriate test for the researchers.
Test and CI for two Variances: Content vs Site
Method
Null hypothesis
Alternative hypothesis
F method was used. This method is accurate for normal data only.
Statistics
Site N St Dev Variance 95% CI for St Devs
1 25 3.067 9.406 (2.195,4.267)
2 25 3.339 11.147 (2.607,4.645)
Ratio of standard deviation =0.191
Ratio of variances=0.844
95% Confidence Intervals
Method CI for St Dev Ratio CI Variance Ratio
F (0.610, 1.384) (0.372, 1.915)
Tests
Method DF1 DF2 Test statistic p-value
F 24 24 0.84 0.681
Corporate sustainability of CPA firms. Refer to the Business and Society (March 2011) study on the sustainability behaviors of CPA corporations, Exercise 2.23 (p. 83). Recall that the level of support for corporate sustainability (measured on a quantitative scale ranging from 0 to 160 points) was obtained for each of 992 senior managers at CPA firms. The accompanying Minitab printout gives the mean and standard deviation for the level of support variable. It can be shown that level of support is approximately normally distributed.
a. Find the probability that the level of support for corporate sustainability of a randomly selected senior manager is less than 40 points.
b. Find the probability that the level of support for corporate sustainability of a randomly selected senior manager is between 40 and 120 points.
c. Find the probability that the level of support for corporate sustainability of a randomly selected senior manager is greater than 120 points.
d. One-fourth of the 992 senior managers indicated a level of support for corporate sustainability below what value?
Descriptive Statistics: Support
Variables | N | Mean | StDev | Variance | Minimum | Maximum | Range |
Support | 992 | 67.755 | 26.871 | 722.036 | 0.000 | 155.000 | 155.000 |
The “last name” effect in purchasing. The Journal of Consumer Research (August 2011) published a study demonstrating the “last name” effect—i.e., the tendency for consumers with last names that begin with a later letter of the alphabet to purchase an item before consumers with last names that begin with earlier letters. To facilitate the analysis, the researchers assigned a number, x, to each consumer based on the first letter of the consumer’s last name. For example, last names beginning with “A” were assigned x = 1; last names beginning with “B” were assigned x = 2; and last names beginning with “Z” were assigned x = 26.
a. If the first letters of consumers’ last names are equally likely, find the probability distribution for x.
b. Find E (x) using the probability distribution, part a. If possible, give a practical interpretation of this value.?
c. Do you believe the probability distribution, part a, is realistic? Explain. How might you go about estimating the true probability distribution for x
A paired difference experiment yielded pairs of observations. In each case, what is the rejection region for testing ?
a.
b.
c.
d.
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