A random sample of n = 755 US cell phone users age 18 and older in May 2011 found that the average number of text messages sentor received per day is 41.5 messages, with standard error about 6.1.1.1Smith, A., "Americans and Text Messaging," Pew Research Center, http://www.pewinternet.org/Reports/2011/Cell-Phone-Texting-2011/Main-Report/How-Americans-Use-Text-Messaging.aspx, accessed September 19, 2011.Your answer is incorrect.(a) Use the information from the sample to give the best estimate of the population parameter.eTextbook and MediaHintYour answer is incorrect.(b) Find a 95% confidence interval for the mean number of text messages.toThe 95 % confidence interval is70°F Sunny Aarch立

Introduction - Confidence interval CI=x±zsnwhere ,x=sample mean z=z-scores=standard deviation…

Answered: A random sample of n = 755 US cell…

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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Bone mineral density (BMD) is a measure of bone strength. Studies show that BMD declines after age 45. The impact of exercise may increase BMD. A random sample of 59 women between the ages of 41 and 45 with no major health problems were studied. The women were classified into one of two groups based upon their level of exercise activity: walking women and sedentary women. The 39 women who walked regularly had a mean BMD of 5.96 with a standard deviation of 1.22. The 20 women who are sedentary had a mean BMD of 4.41 with a standard deviation of 1.02. Which of the following inference procedures could be used to estimate the difference in the mean BMD for these two types of women
A researcher wants to estimate the mean amount of money spentonline by consumers in a particular market. She samples 16 consumers and finds that they spend on average $854 online with a standard deviation of $152. Construct a 99% confidence interval estimate of the mean amount of money spent online. Write a statement that correctly interprets the confidence interval.
Four hundred badminton enthusiasts burn an average of 250 calories playing for an hour with a standard deviation of 36 calories. Estimate the mean caloriesburned in playing badminton at 99% confidence level.
As part of a staged rollout, a new email client was installed on some of the computers of a major company's customer service representatives (CSRS). One of the company's performance analysts has been tasked with estimating the difference on the busiest day of the year between the mean time (in minutes) spent working on email for CSRS using the new email client and the mean time (in minutes) spent working on email for CSRS using the old email client. On the busiest day of the year, the performance analyst studies a random sample of 16 CSRS using the new email client and a random sample of 18 CSRS using the old email client. (These samples are chosen independently.) The analyst records the amount of time (in minutes) each CSR spends working on email. These data are shown in the table. Times working on email (in minutes) New email client 166, 188, 207, 172, 202, 148, 192, 173, 197, 197, 158, 172, 209, 185, 203, 169 Old email client 78, 196, 145, 195, 109, 85, 95, 138, 232, 47, 146, 122,…
According to the American Academy of Sleep Medicine, a healthy adult should obtain at least 7 hours of sleep per night. But is this happening in New York City- aka "the city that never sleeps" ? A study of 28 NYC adults chosen at random found that the sample mean was 6.73 hours and the sample standard deviation was 0.79 hours. Is there statistically significant evidence that NYC adults, on average, sleep less than 7 hours per night? Is the result "practically significant"?
The Fair Isaac Cooperation (FICO) credit score is used by banks and other lenders to determine whether someone is a good credit risk. Scores range from 330 to 850, with a score of 720 or more indicating that a person is a very good credit risk. An economist wants to determine whether the mean FICO score is lower than the cutoff of 720. She finds that a random sample of 60 people had a mean FICO score of 685 with a standard deviation of 80. Can the economist conclude that the mean FICO score is less than 720? Use the a=0.10 level of significance and the P-value method
(b) Two stock markets continuously compounded return series, R1 and R2, are two independent random variables with N(0,2). Another two random variables which are related to R1 and R2, are defined as X=3+R₁ +R₁R₁₂ and Y = 2+ R₁. Determine the covariance, Cov(X,Y). [6]
The Philippine Management Association wishes to have information on the mean income ofmiddle managers in the retail industry. A random sample of 256 managers reveals a samplemean of 45,420. The standard deviation of this sample is 2,050. Construct a 95% confidenceinterval estimate of the true population mean income managers in the retail industry. Interpret your results.

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