Q19. Labor trends were recently studied using a survey of respondents who were either unemployed (A) or employed (B). The survey results revealed that among those surveyed, 70% of those currently unemployed gain employment within the following month, and 30% remain unemployed. Meanwhile, 80% of those currently employed maintain employment through the following month, and 20% become unemployed. Suppose 75% of the population is currently employed. 0.7 0.3 A 0.2 B 0.8

Example 40 A survey asks: Which online services have you used in the last month: Twitter ● Facebook Have used both The results show 40% of those surveyed have used Twitter, 70% have used Facebook, and 20% have used both. How many people have used neither Twitter or Facebook?

C8. According to the Pew Research Center (2015), recent immigrants are better educated than earlier immigrants to the United States. The change was attributed to the availability of better education in each region or country of origin. The percentage of immigrants 25 years of age and older who completed at least high school is reported in this table for 1970 to 2013. Write a statement describing the change over time in the percentage who completed at least a high school degree. 1970 1980 1990 2000 2013 Mexico 14 17 26 30 48 Other Central/South America 57 53 60 66 Asia 75 72 75 82 84 48 68 81 87 95 Europe 36 48 52 58 72 Caribbean 81 91 88 85 85 Africa Source: Pew Research Center, Modern Immigration Wave Brings 59 Million to U.S., Driving Population Growth and Change Through 2065, 2015. Retrieved from https://www.pewresearch.org/hispanic/2015/09/28/modern- immigration-wave-brings-59-million-to-u-s-driving-population-growth-and-change-through-2065/ 52

Determine whether the study depicts an observational study or an experiment.   A scientist was studying the effects of a new fertilizer on crop yield. She randomly assigned half of the plots on a farm to group one and the remaining plots to group two. On the plots in group​ one, the new fertilizer was used for a year. On the plots in group​ two, the old fertilizer was used. At the end of the year the average crop yield for the plots in group one was compared with the average crop yield for the plots in group two.