Set up and solve equations for each of the following business situations. You are planning to advertise your boat for sale on the Internet. The Boat Mart charges $1.30 for a photo plus $0.12 per word. Boat Bargains charges $1.80 for a photo plus $0.10 per word. For what number of words will the charges be the same?
Statistics 350 Fall 2008 Exam 1 Explanations 1. Observe that the distribution is roughly bell-shaped. a. The bulk of the data lies in the 100-120 range, so the median should too and only 110 is reasonable. Another way to see this is to realize that in a symmetric distribution, the mean and median should be the same. b. Since the histogram is bell-shaped, we can apply the empirical rule. Roughly 95% of the measurements lie between 80 and 140. By the empirical rule, these numbers should each be 2 standard deviations from the mean making them 4 standard deviations apart. So, the standard deviation should be (140-80)/4 = 15. c. The sketch is to the right. Since the histogram is bell shaped the quantiles should be approximately equal to the normal quantiles. 2. a. Owning a computer is a categorical variable as the response (‘yes’ or ‘no’) is not a measurement. Time spent using a computer is a quantitative continuous variable since it can be measured and any measurement between 0 and the number minutes in a week makes sense. Which social networking sites a respondent uses is a categorical variable. b. i. The shortest list had about 24 friends on the social networking account, while 75% of the list had at least 177 friends. The value 24 may be an outlier, but is still the shortest listed. In a boxplot, 75% of the data is above (at least) the lower quartile (bottom of the box), here 177
