84 CHAPTER 2 Exploring Data with Tables and Graphs • Carefully identify the value at the center of each histogram. Does there appear to be a difference? (Such comparisons will become much easier and much less subjective in future chapters.) • Write a brief description of your results. Hint: The genders are coded as 1 for male and 0 for female, so sort (arrange in order) all of the rows using the gender column as the basis for sorting. Then the rows for males can be separated from the rows for females by using the copy/paste and cut functions of the software. Cooperative Group Activities 1. Out-of-class activity Record the arrival times of your incoming emails (email timestamps can be used). Then find your email interarrival times and compare the distribution to the author’s email interarrival times which are provided in Review Exercise 1 on page 82. 2. Out-of-class activity Data Set 36 “Fast Food” in Appendix B includes measured service times of different fast food restaurants. Go to one or more fast food restaurants and collect your own service times. Compare the results to those found in Data Set 36 in Appendix B. FROM DATA TO DECISION Were the subjects weighed or did they report their weights? One fascinating aspect of statistics is that we can sometimes learn how data were collected by analyzing the data. Table 2-12 and Table 2-13 both include weights (pounds) of 50 randomly selected adult male subjects. When subjects are included in the National Health and Interview Survey, there is a requirement that subjects must be weighed on a scale. One of the two data sets was obtained by using a scale to actually weigh the subjects, but the other data set consists of weights that were reported by the subjects when they were asked how much they weighed. With a clever use of common sense, we know that when subjects report their weights, the results are often rounded to a value conveniently ending in a 0 or 5. Given this, we are able to deduce how the data were collected by analyzing the last digits of the weights. TABLE 2-12 Weights (lbs) of 50 Adult Males 129 172 115 125 240 124 183 147 195 200 217 180 185 170 217 160 140 232 215 165 196 228 225 165 210 145 200 210 225 200 160 250 185 140 120 250 150 172 200 131 160 205 255 205 145 180 195 230 155 200 TABLE 2-13 Weights (lbs) of 50 Adult Males 155 200 256 166 179 202 170 196 256 165 231 143 174 164 147 200 182 228 195 208 203 125 221 229 130 230 212 218 254 149 129 183 187 212 144 160 199 197 187 144 221 166 174 119 213 158 243 124 226 124 Critical Thinking Use the methods from this chapter to address the following questions. 1. Construct a frequency distribution and histogram of the last digits of the weights in Table 2-12. 2. Construct a frequency distribution and histogram of the last digits of the weights in Table 2-13. 3. Compare the results from questions 1 and 2. Determine which table includes weights obtained by using a scale and which table includes weights that were reported by the subjects. 4. Which table appears to include data that are more accurate? Explain. Big (or Very Large) Data Project Refer to Data Set 45 “Births in New York” in Appendix B, which contains records from 465,506 births. Generate a histogram of the birth weights, then describe the shape of the histogram.
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