91Ó°ÊÓ

The student senate at a university with 15,000 students is interested in the proportion of students who favor a change in the grading system to allow for plus and minus grades (e.g., \(\mathrm{B}+, \mathrm{B}, \mathrm{B}-\), rather than just \(\mathrm{B}\) ). Two hundred students are interviewed to determine their attitude toward this proposed change. What is the population of interest? What group of students constitutes the sample in this problem?

The increasing popularity of online shopping has many consumers using Internet access at work to browse and shop online. In fact, the Monday after Thanksgiving has been nicknamed "Cyber Monday" because of the large increase in online purchases that occurs on that day. Data from a large-scale survey by a market research firm (Detroit Free Press, November 26,2005\()\) was used to compute estimates of the percent of men and women who shop online while at work. The resulting estimates probably won't make most employers happy-42\% of the men and \(32 \%\) of the women in the sample were shopping online at work! Are the estimates given computed using data from a sample or for the entire population?

Heal the Bay is an environmental organization that releases an annual beach report card based on water quality (Heal the Bay Beach Report Card, May 2009 ). The 2009 ratings for 14 beaches in San Francisco County during wet weather were: A+ \(\mathrm{C} \mathrm{B} \mathrm{A} \mathrm{A}+\mathrm{A}+\mathrm{A} \mathrm{A}+\mathrm{B} \mathrm{D} \quad \mathrm{C}^{\mathrm{D}} \mathrm{D} \mathrm{F} \mathrm{F}\) a. Would it be appropriate to display the ratings data using a dotplot? Explain why or why not. b. Summarize the wet weather ratings by constructing a relative frequency distribution and a bar chart. c. The dry weather ratings for these same beaches were: \(\begin{array}{lllllllll}\mathrm{A} & \mathrm{B} & \mathrm{B} & \mathrm{A}+ & \mathrm{A} & \mathrm{F} & \mathrm{A} & \mathrm{A} & \mathrm{A} & \mathrm{A} & \mathrm{A} & \mathrm{A} & \mathrm{B} & \mathrm{A}\end{array}\) Construct a bar graph for the dry weather ratings. d. Do the bar graphs from parts (b) and (c) support the statement that beach water quality tends to be better in dry weather conditions? Explain.

The U.S. Department of Education reported that \(14 \%\) of adults were classified as being below a basic literacy level, \(29 \%\) were classified as being at a basic literacy level, \(44 \%\) were classified as being at an intermediate literacy level, and \(13 \%\) were classified as being at a proficient level (2003 National Assessment of Adult Literacy). a. Is the variable literacy level categorical or numerical? b. Would it be appropriate to display the given information using a dotplot? Explain why or why not. c. Construct a bar chart to display the given data on literacy level.