Spam: A researcher reported that 71.8% of all email sent in a recent month was spam. A system manager at a large corporation believes that the percentageat his company may be 78%. He examines a random sample of 500 emails received at an email server, and finds that 369 of the messages are spam. Canyou conclude that less than 78% of emails are spam? Use both a = 0.10 and a = 0.01 levels of significance and the P-value method and Excel.(a) State the appropriate null and alternate hypotheses.Ho:H₁:This hypothesis test is a (Choose one) test.right tailedleft tailedtwo tailed

Answered: Spam: A researcher reported that 71.8%…

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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A graduate student is interested in how viewing different types of scenes affects working memory. For his study, he selects a random sample of 36 adults. The subjects complete a series of working memory tests before and after walking in an urban setting. Before the walk, the mean score on the test of working memory was 9.1. After the walk, the mean score was 1.4 higher. The graduate student has no presupposed assumptions about how viewing different types of scenes affects working memory, so he formulates the null and alternative hypotheses as: H00 : μDD = 0 H11 : μDD ≠ 0 Assume that the data satisfy all of the required assumptions for a repeated-measures t test. The graduate student calculates the following statistics for his hypothesis test: Mean difference (MDD) 1.4 Estimated population standard deviation of the differences (s) 1.6 Estimated standard error of the mean differences (sMDMD) 0.2667 Degrees of freedom (df) 35 The t statistic 5.25 The critical values of t…
Recent research commissioned by Vodafone suggests that older workers are the happiest employees (BBC News, July 21, 2008). The report documents that 70% of older workers in England feel fulfilled, compared with just 50% of younger workers. A demographer believes that an identical pattern does not exist in Asia. A survey of 120 older workers in Asia finds that 78 feel fulfilled. At a 5% level of significance, test if older workers in Asia feel less fulfilled than their British counterparts. In the box below, answer the following (a) What is the p-value for the test? (Round to three decimal places.) (b) At a 5% level of significance, do older workers in Asia feel less fulfilled than their British counterparts?
A bank wonders if omitting the annual fee for customers who charge at least $4000 per year would increase the amount of credit card usage (i. e. the total amount charged in a year). The bank makes this offer to a random sample of customers that have spent at least $4000. It then compares how much these customers charged this year with how much they charged last year. This data is found on sheet "CC Fees." Is there evidence at a 5% significance level to state that the mean amount increases when the "no-fee" offer was given?
An auto shop wants to examine the proportion of customers that have to return after an appointment. Last year, an examination of 375 customers found that 26.9% had to return after an appointment. You instituted some changes at the auto shop this year, and found from a sample of 430 customers that 33.9% had to return after an appointment. You want to conduct an analysis to determine if there has been an increase in the proportion of customers that need to return after an appointment since the past year, with a significance level of 1%. Using this information, what is the test statistic of your analysis? For the purposes of this analysis, use - Pcurrent year Plast Round any intermediate numbers to four decimal year. places and choose the closest choice to your answer. 2.575 1.03 2.15 1.64 3.30
A 2018 Gallup poll found 20% of adults aged 18 - 29 years vape. Test the claim that the proportion of 18 - 29 year old people who vape has decreased at the 5% significance level. A July 2021 Gallup poll resulted in 17% of the 1,007 of people that age vape.
The Wall Street Journal asked Concur Technologies, Inc., an expense management company, to examine data from 8.3 million expense reports to provide insights regarding business travel expenses. Their analysis of the data showed that New York was the most expensive city. The following table shows the average daily hotel room rate (*) and the average amount spent on entertainment (y) for a random sample of 9 of the 25 most-visited U.S. cities. These data lead to the estimated regression equation ŷ = 17.49 +1.0334x. For these data SSE = 1541.4. Click on the datafile logo to reference the data. Use Table 1 of Appendix B. DATA file City Boston Denver Nashville New Orleans Phoenix San Diego San Francisco San Jose Room Rate ($) 148 96 91 110 90 102 136 90 82 Tampa a. Predict the amount spent on entertainment for a particular city that has a daily room rate of $89 (to 2 decimals). $ Entertainment ($) 161 105 101 142 ***** b. Develop a 95% confidence interval for the mean amount spent on…
A manager claims that fewer than 65% of employees will qualify for performance bonus this year. From a representative sample of 40 employees, 57.5% qualify for performance bonus. Test the manager’s claim at a 1% level of significance.
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Mood variation is related to photoperiod in some people, and the likelihood of depression increases in the winter months. As a result, people often assume that suicide rates increase in winter. A study in Finland (Valtonen et al. 2006) divided the year 1997 into equal halves and compared the number of suicides in “winter” (24 September to 19 March) and “summer” (remainder of year). Out of a total of 1636 suicides, 766 were in winter and 870 were in the summer. Based on these data, estimate the proportion of suicides that occurred in winter, assuming that the suicides were independent. Are the data compatible with a greater suicide rate in winter than summer, based on a 95% confidence interval?
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A team of epidemiologists at the Mayo Clinic wanted to find whether there is an association between obesity and cardiovascular disease (CVD). They conducted a prospective cohort study following obese and non-obese individuals who were free of CVD at the beginning of study for five years. The investigators were also interested in assessing age as a potential confounder, effect modifier, or both. Use the data below to answer the accompanying questions. CVD No CVD Total Obese 10 90 100 Not Obese 35 465 500 Total 45 555 600 CVD No CVD Total Obese 36 164 200 Not Obese 25 175 200 Total 61 339 400 1. Compute the appropriate measure of association for those who were less than age 50. 2. Compute the appropriate measure of association for those who were older or equal to age 50. 3. Compute the crude measure of association? 4. List three attributes that age must satisfy before it could…
The Wall Street Journal asked Concur Technologies, Inc., an expense management company, to examine data from 8.3 million expense reports to provide insights regarding business travel expenses. Their analysis of the data showed that New York was the most expensive city. The following table shows the average daily hotel room rate (X) and the average amount spent on entertainment (Y) for a random sample of 9 of the 25 most-visited U.S. cities. These data lead to the estimated regression equation y = 17.49 + 1.0334x. For these data SSE = 1541.4. Use Table 1 of Appendix B. a. Predict the amount spent on entertainment for a particular city that has a daily room rate of $89 (to 2 decimals). b. Develop a 95% confidence interval for the mean amount spent on entertainment for all cities that have a daily room rate of $89 (to 2 decimals). c. The average room rate in Chicago is $128. Develop a 95% prediction interval for the amount spent on entertainment in Chicago (to 2 decimals).

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