Stat 217 – HW 3

Due Tuesday, Jan .26

To use technology to create dotplots and histograms, use the applets Dotplot Summaries and Histogram Bin Width. To calculate means, medians, standard deviations, and IQRs, you can also use the Dotplot Summaries applet. Just make sure you include screen captures of all relevant output. Don’t just report the values the computer found, show the work!

Note: You may want to make a copy of your assignment for your own reference as you study for the exam. Solutions will be posted Tuesday night.

1) (6 pts) The data in Week1Margins.xls are the margins of victory in college football games involving Top 25 teams for the first weekend of the 2009 season. Note: If the team lost, the loser’s margin is reported as negative (There were a few ranked teams that played each other and a collapse by Florida State; most top teams try to schedule a game against a much weaker opponent for the first week of the season.)

(a) Use the Histogram Binwidth applet to create a histogram of these margins of victory data. Change the binwidth until you find one that feel gives the most effective display of the data.

(b) Write a paragraph describing the distribution of these margins of victory.

(c) How would you expect this distribution to differ later in the season (shape, center, and/or spread), when teams generally play stronger opponents within their conference schedule?

2) Activity 2-18 (p. 30)

3) The file Yankees09.xls contains data on a starting lineup for the 2009 Yankees.

(a) Produce a dotplot (feel free to use technology) of the ages of the Yankees.

(b) Determine the mean and median for the 2009 data. (If using technology, include output.)

(d) Sketch a dotplot (by hand, or move points around in the applet) where the IQR is smaller than in (c) but the standard deviation is larger.

(e) Suppose the lineup stays the same for 2 years. (So every player in the 2009 Yankees lineup is two years older than reported.) What will be the values of the mean and the median in this case? (You can reason through it, or change the data by adding 2 to each value in the technology and recalculate.)

(f) As in (e), what will the value of the IQR be in this case? (Explain or recalculate and include output.)

(g) Suppose the youngest player, Cano, lied when he first joined the league and he is now actually 22 years of age. How will this affect the IQR calculation in (c)? The standard deviation in (c)? (Explain whether each will be larger, smaller, or the same, either explain your reasoning, or make the change and include the new output.)

4) Activity 7-21 (p. 138)

We will discuss Topic 9 in Monday’s class

5) Activity 9-7 (p. 176) part (a) only but explain your reasoning

6) Activity 9-25 (p. 182-8)

For (b), the data can be found in HypoStdDev.xls for use in the Dotplot summaries applet. Copy and paste each column one at a time and save the output computing the actual values.