47) Arthur D. Little, Inc. estimates that approximately 70% of mail received by a household is advertisements (Time, July 14, 1997). A sample of 20 households shows the following data for the number of advertisements received and the total number of pieces of mail received during one week. a) What is the point estimate of the
1. A major department store chain is interested in estimating the average amount its credit card customers spent on their first visit to the chain's new store in the mall. Fifteen credit card accounts were randomly sampled and analyzed with the following results: Χ = $50.50 and s2 = 400. Assuming the distribution of th
Construct a 90% confidence interval for mu sub d, the mean of the differences d for the population of paired data. Assume that the population of paired differences is normally distributed. d-bar = 3.125; s d = 2.911; n = 8 2.435 < <MUµd < 3.815 1.175 < µd < 5.075 2.435 < µd < 5.075
Use the confidence level and sample data to find the margin of error. Systolic blood pressure for women ages 18-24: 94% confidence; n = 81, x-bar = 113.8 mm Hg, sigma = 12.8 mm Hg Round to the nearest one decimal place. 2.7 mm Hg 2.6 mm Hg 42.6 mm Hg 9.0 mm Hg
Construct a confidence interval. See attached file for full problem description.
1. A manufacturer of small appliances employs a market research firm to estimate retail sales of its products by gathering information from a sample of retail stores. This month an SRS of 75 stores in the Midwest sales region finds that these stores sold an average of 24 of the manufacturer's hand mixers, with standard deviatio
Use the confidence level and sample data to find the margin of error E. Weights of eggs: 95% confidence; n = 49, x-bar = 1.70 oz, sigma = 0.33 oz
A researcher wishes to construct a 95% confidence interval for a population mean. She selects a simple random sample of size n=20 from the population. The population is normally distributed and sigma is unknown. When constructing the confidence interval, the researcher should use the t distribution; however, she incorrectly uses
Use the confidence level and sample data to find a confidence interval for estimating the population mean m. Test scores: n = 101, x-bar = 96.8, sigma = 8.3, 99 percent confidence
The following confidence interval is obtained for a population proportion, p:(0.458, 0.490). Use these confidence interval limits to find the point estimate, p-hat.
1. TFQ: Amy wants to find a 96% confidence interval for the amount of time it takes to get to work. She kept records for 35 days and found her average time to commute to work was 20.5 minutes with a standard deviation of 3.6 minutes. Amy's maximum error of estimate would be 1.25 minutes. 2. TFQ: Charles wants to be 90% c
Question 1: Find the number of successes x suggested by the given statement. Among 680 adults selected randomly from among the residents of one town, 27.2% said that they favor stronger gun-control laws. a. 183 b. 184 c. 186 d. 185 Solve the problem. In a game, you have a 1/29 probabilit
* Construct the indicated confidence interval for the difference between population proportions p1 - p2. Assume that the samples are independent and that they have been randomly selected. x1 = 57, n1 = 95 and x2 = 84, n2 = 96; Construct a 98% confidence interval for the difference between population proportions p1 - p2. ....
1) In a poll to estimate presidential popularity, each person in a random sample of 1,000 voters was asked to agree with one of the following statements: 1. The President is doing a good job. 2. The President is doing a poor job. 3. I have no opinion. A total of 560 respondents selected the first statement, indicating
1) The following is sample information. Test the hypothesis that the treatment mean are equal. Use the .05 significance level. Treatment 1 Treatment 2 Treatment 3 8 3 3 11 2 4 10 1 5 3 4 2 T1= 29 T2= 11 T3= 16 TOTAL T=56 N1= 3 N=5 N=4 N=12 9.6 (MEAN) 2.2 (MEAN) 4 (MEAN) 15.8 FOR GRAND MEAN A. State the
The table gives the average low tempatures in January and July for twelve cities. Construct a 99% confidence interval for the mean temperature difference (January-July) between winter and summer. Assume the population are normally distributed. Cities JANUARY JULY Chhose the 99% confidence interval for the mean diffe
In regards to the stock market returns, what is the significance of the Law of Large Numbers? What do confidence intervals represent? What are the differences between z-statistics and t-statistics?
Multiple choice: confidence interval for the population proportion, probability distribution, probability calculation
1. Elwin Osbourne, CIO at GFS, Inc., is studying employee use of GFS e-mail for non-business communications. A random sample of 200 e-mail messages was selected. Thirty of the messages were not business related. The 95% confidence interval for the population proportion is _________. a.0.091 to 0.209 b. 0.108 to 0.192
a) A seed distributor guarantees 95% germination of the seeds he supplies. A retailer has an agreement with the distributor, under which he may test a random sample of 200 seeds for germination and send the whole batch back to the manufacturer if the proportion of germinating seeds is significantly below 95%. With a significance
(See attached file for full problem description with proper equations) An engineer was interested in comparing the variability of the power of a laser at current levels of 16 amps (X) and 20 amps (Y). To do so, random samples of 25 observations of power readings were obtained at each current level. The samples were taken hi
1. You are the manager of a tax preparation center. A vendor brings in a new software package that he says can reduce the amount of time spent preparing taxes. What would your null hypothesis be? With your null who is bearing the risk of Type I and Type II errors? 2. What is the value of establishing confidence intervals
2. A company manufactures steel bolts that continuously feed an assembly line downstream. Historically, the thickness of these bolts follows a normal distribution with a standard deviation of 1.6 mm. A recent random sample of 10 observations yielded these values of thickness, in mm: 9.7 9.9 10.3 10.1 10.5 9.4 9.9 10.1
Refer to the sample results below for the measured nicotine contents of randomly selected filtered and non-filtered king-size cigarettes. All measurements are in milligrams. a. use a 0.05 significance level to test the claim that king-size cigarettes with filters have a lower mean amount of nicotine than the mean amount of nic
A discount store is trying to decide whether to use a single waiting line for available cashiers. The waiting times for 25 randomly selected customers was found to have a standard deviation of 1.7 minutes. Construct a 95% confidence interval for the population variance.
A College wished to know the number of library books borrowed by students over a term. 16 students were selected at random and the following data were obtained for the books they borrowed: 24, 22, 25, 25, 21, 26, 27, 22, 24, 23, 28, 23, 28, 25, 26, 21 (i) Calculate a 95% confidence interval for the population mean, . (ii)
8.54 Alice Chang and her colleagues (A. Chang, T. L. Rosenthal, R. H. Bryant, R. H. Rosenthal, R. M. Heidlage, and B. K. Fntzlcr. "Comparing High School and College Students' L.eisure In- wrests and Stress Ratings," Behavioral Research Therapy 31(2), 1993) tested 559 high school students using a leisure-interest checklist (LIC)
Working with Binomial Distribution to find the sample size needed for the margin of error to be no higher than a given percent.
Consider the case where we have n observations, sampled from a binomial pdf (our parameter estimator can therefore be given by X/n). Assume that the margin of error is 6%. How many observations do we need for the margin of error for the proportion to be cut in half (to 3%)?
Smith Travel Research provides information on the one-night cost of hotel rooms throughout the United States (USA today, July 8, 2002). Use $2 as the desired margin of error and $22.50 as the planning value of the population standard deviation to find the sample size recommended in (a), (b), and (c). a. Determine a 90% confid
Fifteen patients who suffer from high blood pressure were given a drug that is supposed to lower blood pressure. If X denotes the amount of a patient's decrease from his or her normal blood pressure and if the sample from 15 produced the estimate = 5 and s = 8, find a 95 percent confidence interval for using small sample meth
(See attached file for full problem description with proper symbols) --- Two sets of 100 students each were taught to read by two different methods. After instruction was over a reading test gave the following results: = 73.4, = 70.3, = 8, =10. Show that a 90 percent confidence interval for is