First I would like to say that im surprised i havent found a forum like this until now, im very excited to help others with their math problems (the most i can atleast) as much as i am excited to get other peoples help I would really appreciate help on these questions; I have posted the questions i am doing and the answers I have, if anyone can confirm/deny how correct I am and help accordingly that would be extremely appreciated.
Just doing questions in my text book for my econ statistics class in preparation for the midterm and for some reason am stuck on this question. From what i understand the best "interval" system to use is a Z-score, but with the information given how do i apply it?
z = (X - U)/ O
x = raw score (which would be what in this case?)
U = mean
O = standard deviation
I have the standard deviation and mean (12.02 and 4.25) but whats the raw score? and how do i expect the distribution to be?
2.76 Blogs for Fortune 500 firms. Refer to the Journal of Relationship Marketing (Vol. 7, 2008) study of the preva- lence of blogs and forums at Fortune 500 firms with both English and Chinese Web sites, Exercise 2.9 (p. 40). In a sample of firms that provide blogs and forums as market- ing tools, the mean number of blogs/forums per site was 4.25, with a standard deviation of 12.02.
a. Provide an interval that is likely to contain the number of blogs/forums per site for at least 75% of the Fortune 500 firms in the sample.
b. Do you expect the distribution of the number of blogs/forums to be symmetric, skewed right, or skewed left? Explain.
2.9 Blogs for Fortune 500 firms. Web site communication through blogs and forums is becoming a key marketing tool for companies. The Journal of Relationship Marketing (Vol. 7, 2008) investigated the prevalence of blogs and fo- rums at Fortune 500 firms with both English and Chinese Web sites. Of the firms that provided blogs/forums as a marketing tool, the accompanying table gives a breakdown on the entity responsible for creating the blogs/forums. Use a graphical method to describe the data summarized in the table. Interpret the graph.
Created by company 38.5
Created by employees 34.6
Created by third party 11.5
Creator not identified 15.4
Social networking Web sites in the United Kingdom. In the United States, MySpace and FaceBook are considered the two most popular social networking Web sites. In the United Kingdom (UK), the competition for social net- working is between MySpace and Bebo. According to Nielsen/NetRatings (April 2006), 4% of UK citizens visit MySpace, 3% visit Bebo, and 1% visit both MySpace and Bebo.
a. DrawaVenndiagramtoillustratetheuseofsocialnet- working sites in the United Kingdom.
b. Find the probability that a UK citizen visits either the MySpace or Bebo social networking sites.
c. Useyouranswertopartbtofindtheprobabilitythata UK citizen does not visit either social networking site.
Guilt in decision making. The effect of guilt emotion on how a decision maker focuses on the problem was investigated in the Jan. 2007 issue of the Journal of Behavioral Decision Making (see Exercise 1.26, p. 24). A total of 171 volunteer students participated in the experiment, where each was randomly assigned to one of three emotional states (guilt, anger, or neutral) through a reading/writing task. Immediately after the task, students were presented with a decision problem where the stated option has predomi- nantly negative features (e.g., spending money on repairing a very old car). The results (number responding in each cat- egory) are summarized in the accompanying table. Suppose one of the 171 participants is selected at random.
Monitoring quality of power equipment. Mechanical Engineering (Feb. 2005) reported on the need for wireless networks to monitor the quality of industrial equipment. For example, consider Eaton Corp., a company that develops dis- tribution products. Eaton estimates that 90% of the electrical switching devices it sells can monitor the quality of the power running through the device. Eaton further estimates that of the buyers of electrical switching devices capable of monitor- ing quality, 90% do not wire the equipment up for that pur- pose. Use this information to estimate the probability that an Eaton electrical switching device is capable of monitoring
power quality and is wired up for that purpose.
Choosing portable grill displays. Refer to the Journal of Consumer Research (Mar. 2003) marketing study of influ- encing consumer choices by offering undesirable alterna- tives, Exercise 3.21 (p. 130). Recall that each of 124 college students selected showroom displays for portable grills. Five different displays (representing five different-sized grills) were available, but the students were instructed to select only three displays in order to maximize purchases of Grill #2 (a smaller-sized grill). The table shows the grill dis- play combinations and the number of times each was se- lected by the 124 students. Suppose one of the 124 students is selected at random. Let x represent the sum of the grill numbers selected by this student. (This value is an indicator of the size of the grills selected.)
What is the probability that x exceeds 10?
Appeals of federal civil trials. Refer to the Journal of the American Law and Economics Association (Vol. 3, 2001) study of appeals of federal civil trials, Exercise 3.41 (p. 140). A breakdown of the 678 civil cases that were originally tried in front of a judge (rather than a jury) and appealed by either the plaintiff or defendant is repro- duced in the next table. Suppose each civil case is awarded points (positive or negative) based on the out- come of the appeal for the purpose of evaluating federal judges. If the appeal is affirmed or dismissed, +5 points are awarded. If the appeal of a plaintiff trial win is re- versed, -1 point is awarded. If the appeal of a defendant trial win is reversed, -3 points are awarded. Suppose one of the 678 cases is selected at random and the number, x, of points awarded is determined. Find and graph the probability distribution for x.