91Ó°ÊÓ

For each lettered part, a through c, examine the two given sets of numbers. Without doing any calculations, decide which set has the larger standard deviation and explain why. Then check by finding the standard deviations by hand. $$ \begin{array}{ll} {\text { Set 1 }} & {\text { Set 2 }} \\ \hline \text { a) } 4,7,7,7,10 & 4,6,7,8,10 \\ \text { b) } 100,140,150,160,200 & 10,50,60,70,110 \\ \text { c) } 10,16,18,20,22,28 & 48,56,58,60,62,70 \end{array} $$

Create a stem-and-leaf display for these horsepowers of autos reviewed by Consumer Reports one year, and describe the distribution: \(\begin{array}{rrrrr} 155 & 103 & 130 & 80 & 65 \\ 142 & 125 & 129 & 71 & 69 \\ 125 & 115 & 138 & 68 & 78 \\ 150 & 133 & 135 & 90 & 97 \\ 68 & 105 & 88 & 115 & 110 \\ 95 & 85 & 109 & 115 & 71 \\ 97 & 110 & 65 & 90 & \\ 75 & 120 & 80 & 70 & \end{array}\)

Two researchers measured the pH (a scale on which a value of 7 is neutral and values below 7 are acidic) of water collected from rain and snow over a 6-month period in Allegheny County, PA. Describe their data with a graph and a few sentences: \(\begin{array}{lllllllll}4.57 & 5.62 & 4.12 & 5.29 & 4.64 & 4.31 & 4.30 & 4.39 & 4.45 \\ 5.67 & 4.39 & 4.52 & 4.26 & 4.26 & 4.40 & 5.78 & 4.73 & 4.56 \\\ 5.08 & 4.41 & 4.12 & 5.51 & 4.82 & 4.63 & 4.29 & 4.60 & \end{array}\)