Example: Home mortgage interest rates for 30-year fixed rate loans vary throughout thecountry. During the summer of 2000, data available from various parts of the countrysuggested that the standard deviation of the interest rates was .096. The correspondingvariance in interest rates would be (096) =.009216. Consider a follow up study in thesummer of 2005. The interest rates for 30 year fixed rate loans at a sample of20 lendinginstitutions had a sample standard deviation of .114. Conduct a hypothesis test usingH:o = .009216 to see whether the sample data indicate that the variability in interest rateschanged. Use a = .05. What is your conclusion?

Answered: Example: Home mortgage interest rates…

MATLAB: An Introduction with Applications

6th Edition

ISBN:9781119256830

Author:Amos Gilat

Publisher:Amos Gilat

Chapter1: Starting With Matlab

Section: Chapter Questions

Problem 1P

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1.Suppose a used car dealer runs autos through a two-stage process to get them ready to sell. The mechanical checkup costs $50 per hour and takes an average of 90 minutes, with a standard deviation of 15 minutes. The appearance prep (wash, polish, etc.) costs $6 per hour and takes an average of 60 minutes, with a standard deviation of 5 minutes. What are the mean and standard deviation of the total time spent preparing a car? (Note that we cannot find the standard deviation if we do not believe that the two phases of the process are independent, an important assumption to check.) b). What are the mean and standard deviation of the total expense to prepare a car? c). What are the mean and standard deviation of the difference in costs for the two phases of the operation? d). What is the probability that it will take longer to do the appearance prep than the mechanical checkup? (Note that we cannot answer this question unless we believe each phase of the process can be described by a…
In a mid-size company, the distribution of the number of phone calls answered each day by each of the 12 receptionists is bell-shaped and has a mean of 38 and a standard deviation of 8. Using the Standard Deviation Rule (as presented in the book), what is the approximate percentage of daily phone calls numbering between 30 and 46?
Based on a recent study, the pH level of the arterial cord (one vessel in the umbilical cord) is normally distributed with mean 7.27and standard deviation of 0.11. Find the percentage of preterm infants who have the following arterial cord pH levels. a. pH levels between 7.00 and 7.50. b. pH levels over 7.35. a. The percentage of arterial cord pH levels that are between 7.00and 7.50 is __________%. (Round to two decimal places as needed.) b. The percentage of arterial cord pH levels that are over 7.35 is _______%. (Round to two decimal places as needed.)
A marketing researcher wants to estimate the mean amount spent per year ($) on a web site by membership member shoppers. Suppose a random sample of 100 membership member shoppers who recently made a purchase on the web site yielded a mean amount spent of $55 and a standard deviation of $52. Complete parts (a) and (b) below. a. Is there evidence that the population mean amount spent per year on the web site by membership member shoppers is different from $51? (Use a 0.01 level of significance.) State the null and alternative hypotheses. Ho: H (Type integers or decimals. Do not round. Do not include the $ symbol in your answer.) Identify the critical value(s). The critical value(s) is/are (Type an integer or a decimal. Round to two decimal places as needed. Use a comma to separate answers as needed.) Determine the test statistic. The test statistic, 1STAT, is (Type an integer or a decimal. Round to two decimal places as needed.) State the conclusion. Ho. There is evidence that the…
A marketing researcher wants to estimate the mean amount spent per year ($) on a web site by membership member shoppers. Suppose a random sample of 100 membership member shoppers who recently made a purchase on the web site yielded a mean amount spent of $58and a standard deviation of $55.Complete parts (a) and (b) below. a. Is there evidence that the population mean amount spent per year on the web site by membership member shoppers is different from $51? (Use a 0.01 level of significance.) State the null and alternative hypotheses.
A company produces widgets with a mean weight of 10 ounces and a standard deviation of 0.5 ounces. If the weight of widgets is normally distributed, what percentage of widgets weigh between 9.5 and 11 ounces?
The National Football League franchise owners and the National Football League Player's Association (a union representing NFL players) are currently negotiating over terms.for the upcoming season. One of the proposals is to increase the number of regular season games per year from 16 to 17. Will the new balanced standard deviation of win percentage for à 17-game season be higher or lower than the previous balanced standard deviation in the 16-game season? Why?
3) A SRS of 25 of the same model of car results in an annual mean maintenance cost of $575 and a standard deviation of $58. A car sales person claims the annual mean maintenance cost of that model is less than $600. Test the claim with a = .01.
A new phone system was installed last year to help reduce the expense of personal calls that were being made by employees. Before the new system was installed, the amount being spent on personal calls follows a normal distribution with an average of $400 per month and a standard deviation of $50 per month. Refer to such expenses as PCEʹs (personal call expenses). Find the point in the distribution below which 2.5% of the PCEʹs fell.
4. The cost of a daily newspaper varies from city to city. However, the variation among prices remains steady with a standard deviation of 18¢. A study was done to test the claim that the mean cost of a daily newspaper is $1.00. Twelve costs yield a mean cost of 93¢ with a standard deviation of 17¢. Do the data support the claim at the 1% level?
Pulse rates (in bpm) were collected from a random sample of females who are non-smokers but do drink alcohol. The pulse rates before they exercised had a mean of 75.08 and a standard deviation of 10.75. The pulse rates after they ran in place for one minute had a mean of 125.43 and a standard deviation of 25.92.The pulse rates before they exercised were than the pulse rates after they ran in place for one minute.
1) A half-century ago, the mean height of women in a particular country in their 20s was 63.7 inches. Assume that the heights of today's women in their 20s are approximately normally distributed with a standard deviation of 2.31 inches. If the mean height today is the same as that of a half-century ago, what percentage of all samples of 26 of today's women in their 20s have mean heights of at least 65.04 inches?

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