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ECON 249 FINAL
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Terms in this set (17)
A survey of investors finds that 60% use a full-service brokerage firm to invest in stocks, 30% trade stocks online and 24% do both. The probability that an investor selected at random uses a full-service brokerage firm or trades stocks online is
66%
60+30-24=66
An advocacy group is investigating whether gender has an effect on job categories in large investment firms. She surveyed a sample of firms with the following results:
job category male female
clerical/technical 85 215
professional staff 720 480
executive/managerial 400 100
What is the probability that a randomly selected employee's job category is executive/managerial given that she is female?
0.13
100/795=.13
An advocacy group is investigating whether gender has an effect on job categories in large investment firms. Given the results shown in the table below, which of the following statements is true about gender and job category?
job category male female
clerical/technical 85 215
professional staff 720 480
executive/managerial 400 100
Gender and job category are not independent
The number of claims for lost luggage in a small city airport averages nine per day. Assuming the Poisson distribution, what is the probability that there will be fewer than 3 claims on any given day?
0.0062
In a particular production process, drying times for newly pained parts are uniformly distributed between 2 and 8 minutes. The probability that a part dries in less than 6 minutes is
4/8
A men's clothing store has determined the following probability distribution for the number of special size orders placed per month. Based on distribution, the standard deviation in the number of special size orders placed per month is
Numbers Ordered Probability
0 .10
5 .10
10 .12
15 .30
20 .38
6.6
Insurance company records indicate that 10% of its policyholders file claims involving theft or robbery of personal property from their homes. Suppose a random sample of 400 policyholders is selected. The standard deviation of the sampling distribution of the sample proportion of policyholders filing claims involving theft or robbery from their homes is
0.015
A researcher is conducting a study on eating disorders. Using a list of recent participants in the online Weight Watchers program, she randomly selects a name from the alphabetized list. She then chooses every tenth person from that point on to include in her study. The sampling strategy is called
Systematic
A researcher is conducting a study on eating disorders. Using a list of recent participants in the online Weight Watchers program, she randomly selects a sample from the alphabetical list. The list represents the
Sampling frame
A researcher is conducting a study to determine how knowledgeable teenagers are about making good food choices. She decides to interview teenagers eating at a fast food restaurant. The results may be biased because this is a
convenience sample
We have calculated a 95% confidence interval and would prefer for our next confidence interval to have a smaller margin of error without losing any confidence. In order to do this, we can
I. change the z value to a smaller number
II. take a larger sample
III. take a smaller sample
II only
In economic downturns, companies attempt to downsize their workforces by offering early retirement incentives to older employees. A survey of 723 companies found that 195 engage in such downsizing practices. The 99% confidence interval for the proportion of companies that downsize their workforces by offering early retirement incentives is
0.23 to 0.31
Suppose the time it takes for a purchasing agent to complete an online ordering process is normally distributed with a mean of 8 minutes and a standard deviation of 2 minutes. Suppose a random sample of 25 ordering processes is selected. The standard deviation of the sampling distribution of mean times is
0.4 minutes
Suppose the time it takes for a purchasing agent to complete an online ordering process is normally distributed with a mean of 8 minutes and a standard deviation of 2 minutes. Suppose a random sample of 25 ordering processes is selected. What is the probability that the sample mean will be less than 7.5 minutes?
0.8944
Assume that a set of test scores in an Introduction of Finance class is normally distributed with a mean of 72 and a standard deviation of 8. Use the 68-95-99-7 rule to find the percentage of scores less than 56.
2.5%
Assume that a set of test scores in an Introduction of Finance class is normally distributed with a mean of 72 and a standard deviation of 8. Use the 68-95-99-7 rule to find the percentage of scores between 64 and 88.
95%
Speeds of cars were measured as they passed one point on a road to study whether traffic speed controls were needed. Here's a histogram and boxplot of the measured speeds. Accurate statements about this distribution include:
Both A and C
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Verified questions
STATISTICS
Test the claim about the difference between two population means $$ \mu _ { 1 } $$ and $$ \mu _ { 2 } $$ at the level of significance $$ \alpha $$ . Assume the samples are random and independent, and the populations are normally distributed. If convenient, use technology. Claim: $$ \mu _ { 1 } \leq \mu _ { 2 }; \alpha = 0.05 $$ . Assume $$ \sigma _ { 1 } ^ { 2 } \neq \sigma _ { 2 } ^ { 2 } $$ . Sample statistics: $$ \overline { x } _ { 1 } = 183.5, s _ { 1 } = 1.3, n _ { 1 } = 25 $$ and $$ \overline { x } _ { 2 } = 184.7, s _ { 2 } = 3.9, n _ { 2 } = 25 $$
STATISTICS
(a) Identify the claim and state $$ H _ { 0 } $$ and $$ H _ { a } $$ . (b) Determine whether the hypothesis test is left-tailed, right-tailed, or two-tailed, and whether to use a z-test or a t-test. Explain your reasoning. (c) Find the critical value(s) and identify the rejection region(s). (d) Find the appropriate standardized test statistic. If convenient, use technology. (e) Decide whether to reject or fail to reject the null hypothesis. (f) Interpret the decision in the context of the original claim. A marine biologist claims that the mean girth of male harbor seals is different from the mean girth of female harbor seals. The mean girth of a random sample of 16 male harbor seals is 97 centimeters with a standard deviation of 19 centimeters. The mean girth of a random sample of 14 female harbor seals is 93 centimeters with a standard deviation of 16 centimeters. At $$ \alpha = 0.01 $$ , can you support the marine biologist's claim? Assume the populations are normally distributed and the population variances are equal.
STATISTICS
(a) identify the claim and state $$ H _ { 0 } $$ and $$ H _ { a } $$ , (b) use technology to find the P-value, (c) decide whether to reject or fail to reject the null hypothesis, and (d) interpret the decision in the context of the original claim. Assume the population is normally distributed. A marine biologist claims that the mean dive duration of a harbor seal in Monterey Bay is at least 5.8 minutes. A random sample of 35 dive durations has a mean of 4.9 minutes and a standard deviation of 1.8 minutes. Is there enough evidence to reject the claim at $$ \alpha = 0.01 $$ ?
PROBABILITY
Brent borrowed $3000 from his brother Dave. He agreed to repay the money at the end of 2 years, giving Dave the same amount of interest that he would have received if the money had been invested at 1.75% compounded quarterly. How much money did Brent repay his brother?