Page 70 - Demo

30 Chapter 1 %u2022 Analyzing One-Variable DataHousehold size0 5 10 15 20 25 30South AfricaHousehold sizeUnited Kingdom0 5 10 15 20 25 30SOLUTION: Shape: The distribution of household size for the South Africa sample is skewed to the right, with a single peak at 4 people and a clear gap between 15 and 26 people. The distribution of household size for the U.K. sample is roughly symmetric, with a single peak at 4 people. Outliers: There are no obvious outliers in the U.K. dotplot. The two largest values in the South Africa dotplot%u2014households with 15 and 26%u00a0people%u2014appear to be outliers. Center: Household sizes for the South Africa sample tend to be larger (median = 6 people) than for the U.K. sample (median%u00a0 = 4 people). Variability: The household sizes for the South Africa sample vary more (from 3 to 26 people) than for the U.K. sample (from 2%u00a0to 6 people). FOR PRACTICE TRY EXERCISE 17. When comparing distributions of a quantitative variable, you must include more than just the group names (South Africa, United Kingdom) to achieve context. You also need to include the variable name (household size). When comparing distributions of quantitative data, it%u2019s not enough just to list values for the center and variability of each distribution. You have to explicitly comparethese values, using expressions like %u201cgreater than,%u201d %u201cless than,%u201d or %u201cabout the same as.%u201d You can use the One Quantitative Variable, Multiple Groups applet at stapplet.com to make parallel dotplots for comparing the distribution of a quantitative variable in two or more groups. YO U R TU R N LE SSO N 1. 3 How can we check the health of a stream? Nitrates are organic compounds that are a main ingredient in fertilizers. When those fertilizers are washed into streams, the nitrates can have a toxic effect on fish. An ecologist studying nitrate pollution in two streams measures nitrate concentration at 42 places on Stony Brook and 42 places on Mill Brook. The parallel dotplots display the data. goodluz/Shutterstock%u00a9 Bedford, Freeman & Worth Publishers. For review purposes only. Do not distribute.