Educational Technology, Inc. sells software to provide guided homework problems for a statistics course. They would like to know if students who use the software score better on exams. A sample of students who used the software had the following exam scores: 86, 78, 66, 83, 84, 81, 84, 109, 65, and 102. Students who did not use the software had the following exam scores: 91, 71, 75, 76, 87, 79, 73, 76, 79, 78, 87, 90, 76, and 72. Assume the population standard deviations are not the same. At the .10 significance level, can we conclude that there is a difference in the mean exam scores for the two groups of students?

On a random basis, Bob buys a small take-out coffee from one of two restaurants. As a statistics project in the month of May, he measured the temperature of each cup immediately after purchase, using an analog cooking thermometer. Assuming equal variances, is the mean temperature higher at Panera than at Bruegger's at $\alpha=.01$ ? Note: Ideal coffee temperature is a matter of individual preference (see www.coffeedetective.com). Coffee

$$\begin{array}{lllllllllllll}\text { Panera } & 171 & 161 & 169 & 179 & 171 & 166 & 169 & 178 & 171 & 165 & 172 & 172 \\ \text { Bruegger's } & 168 & 165 & 172 & 151 & 162 & 158 & 157 & 160 & 158 & 160 & 158 & 164\end{array}$$

What is the key concept for this section? Describe four ways to manage forests more sustainably. What is certified sustainably grown timber? What are four ways to reduce the harm caused by forest fires to forests and to people? What is a prescribed fire? What are three ways to reduce the need to harvest trees? Describe the global fuelwood crisis. What are five ways to protect tropical forests and use them more sustainably? Describe the efforts by Wangari Maathai and the Green Belt Movement to restore forests.

The amount of sea ice in the Arctic shrank dramatically this summer and is now smaller than it has been in a century of record-keeping, new research reveals. Scientists say rising temperatures brought on by human-made global warming is probably to blame for the melting trend. Most scientists attribute this warming to human activities such as burning fossil fuels. The shift could lead to increased coastal erosion and shrinking of habitat for animals like polar bears. Melting sea ice may lead to greater coastal erosion, because Arctic storms could produce much larger waves on the open ocean. As the sea ice continues to melt, polar habitat also continues to shrink. If the decline in sea ice continued, summers in the Arctic could become completely ice-free before the end of this century, scientists warn.

How could melting sea ice possibly lead to greater coastal erosion?

A. Polar bears would use more of the land.

B. Humans would use the exposed land for fossil fuels.

C. It would increase global temperatures, ruining the land.

D. Arctic storms could produce larger waves to erode the shoreline.

A statistics instructor wonders whether significant differences exist in her students' median exam scores in her three different sections. She randomly selects scores from 10 different students in each section. A portion of the data is shown 7 in the accompanying table.

$$\begin{array}{|c|c|c|} \hline \text { Section 1 } & \text { Section 2 } & \text { Section 3 } \\ \hline 85 & 91 & 74 \\ \hline 68 & 84 & 69 \\ \hline \vdots & \vdots & \vdots \\ \hline 74 & 75 & 73 \\ \hline \end{array}$$

Do these data provide enough evidence at the $5 \%$ significance level to indicate that there are some differences in median scores in the three sections?

Corporate sustainability of CPA firms. Refer to the Business and Society (March 2011) study on the sustainability behaviors of CPA corporations, Exercise $2.48$ (p. 72). Numerical measures of variation for level of support for the 992 senior managers are shown in the accompanying Minitab printout. Locate the range on the printout. Comment on the accuracy of the statement: "The difference between the largest and smallest values of level of support for the 992 senior managers is 155 points."

$$\begin{aligned} &\text { Descriptive Statistics: Support }\\ &\begin{array}{lrrrrrrr} \text { Vasiable } & \text { M } & \text { Mean } & \text { StDev } & \text { Vaxatance } & \text { Minamun Maximum Range } \\ \text { Supbort } 992 & 67.755 & 26.872 & 722.036 & 0.000 & 255.000 & 255.000 \\ \hline \end{array} \end{aligned}$$

The Bureau of Labor Statistics reports a $6.0 \%$ unemployment rate for Americans whose maximum attained a level of education is a high school diploma. Is the unemployment rate significantly different for Americans who have earned their bachelor's degrees? Suppose we have a random sample of 500 Americans whose maximum attained a level of education is a bachelor's degree and found 18 who are unemployed. Use these sample results to conduct a hypothesis test to determine whether the unemployment rate for Americans whose maximum attained a level of education is a bachelor's degree differs significantly from the unemployment rate for Americans whose maximum attained level of education is a high school diploma.

b. Use the sample results to compute the test statistic and the $p$-value.

The Wechsler IQ test is designed so that the mean is 100 and the standard deviation is 15 for the population of normal adults. Find the sample size necessary to estimate the mean IQ score of statistics students. We want to be 95% confident that our sample mean is within 2 IQ points of the true mean. The mean for this population is clearly greater than 100. The standard deviation for this population is probably less than 15 because it is a group with less variation than a group randomly selected from the general population; therefore, if we use $\sigma=15$, we are being conservative by using a value that will make the sample size at least as large as necessary. Assume then that $\sigma=15$ and determine the required sample size.

Complete each statement using the correct word or words from the vocabulary list. The image on a television screen is produced by a _________.

$$\begin{matrix} \text{carrier wave } & \text{microwaves}\\ \text{cathode-ray tube } & \text{photon}\\ \text{electromagnetic wave } & \text{radiant energy }\\ \text{gamma rays } & \text{radio waves }\\ \text{Global Positioning System } & \text{transceiver}\\ \text{infrared waves } & \text{ultraviolet waves }\\ & \text{visible light }\\ & \text{X rays }\\ \end{matrix}$$

Choose the best answer. It has been projected that aquaculture could supply about one-half the global demand for seafood by 2025. However, future production through aquaculture could be limited because (a) concentrated waste from aquaculture facilities contaminates rivers and oceans. (b) raising fish in a protected environment could lead to a fish population overshoot. (c) the economies of developing countries would be negatively affected. (d) ocean fishing operations would go out of business.

The Navstar Global Positioning System (GPS) utilizes a group of 24 satellites orbiting the Earth. Using "triangulation" and signals transmitted by these satellites, the position of a receiver on the Earth can be determined to within an accuracy of a few centimetres. The satellite orbits are distributed evenly around the Earth, with four satellites in each of six orbits, allowing continuous navigational "fixes." The satellites orbit at an altitude of approximately $11,000$ nautical miles [$1$ nautical mile $=$ $1.852 \mathrm{~km}=6076 \mathrm{~ft}]$.Find the speed of each satellite.

How could changes in Earth's tilt influence global climate?

A. A high angle of tilt causes snow and ice to fall off the planet.

B. A minimum angle of tilt causes high latitudes to receive less sunlight during the summer, causing an increase in glaciers.

C. A maximum angle of tilt causes Earth to reflect more sunlight into space, causing an increase in glaciers.

D. A high angle of tilt causes the continents to move away from the poles leading to more glaciers.

Color and clarity of diamonds. Diamonds are categorized according to the "four C's": carats, clarity, color, and cut. Each diamond stone that is sold on the open market is provided a certificate by an independent diamond assessor that lists these characteristics. Data for 308 diamonds were extracted from Singapore's Business Times (Journal of Statistics Education, Vol. 9, No. 1, 2001). Color is classified as $\mathrm{D}, \mathrm{E}, \mathrm{F}, \mathrm{G}, \mathrm{H}$, or I, while clarity is classified as IF, VVS1, VVS2, VS1, or VS2. In addition to color and clarity, the independent certification group (GIA, HRD, or IGI), the number of carats and the asking price were recorded. Find and interpret the mean of the data set.

The following table shows key operating statistics for the four largest public accounting firms:

$$\begin{array}{lccc} & \begin{array}{c} \textbf { U.S. Net } \\ \textbf { Revenues } \\ \textbf { (in millions) } \end{array} & \begin{array}{c} \textbf { No. of } \\ \textbf { Partners } \end{array} & \begin{array}{c} \textbf { No. of } \\ \textbf { Professional } \\ \textbf { Staff } \end{array} \\ \hline \text { Deloitte \& Touche } & \$ 10,980 & 2,949 & 32,857 \\ \text { Ernst \& Young } & 8,232 & 2,350 & 20,250 \\ \text { PricewaterhouseCoopers } & 7,578 & 2,198 & 22,100 \\ \text { KPMG LLP } & 5,679 & 1,818 & 16,564 \end{array}$$

a. Determine the revenue per partner and revenue per professional staff for each firm. Round to the nearest dollar.