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Name Elizabeth Tice Date Period Conditional Probability & Independence Worksheet 1. A 2014 survey suggests that 71% of US teenagers use Facebook, 33% use Twitter, and 15% do both. A) Suppose we select a US teenager at random and learn that the student uses Facebook. Find the probability that the student uses twitter. B) Are the events "using Facebook" and "using Twitter" independent? Justify your answer. 2. A recent census at a major university revealed that 60% of its students mainly used Macs. The rest primarily used PCs. At the time of the census, 67% of the school's students were undergraduates. The rest were graduate students. In the census, 23% of respondents were graduate students who said that they used Macs as their primary computers. A) Suppose we select a student at random and learn that the student mainly uses a Mac. Find the probability that this person is a graduate student. B) Are the events "using a Mac" and "being a graduate student" independent? Justify your answer. 3. The 28 students in Mr. Tabor's statistics class completed a brief survey. One of the questions asked whether each student was right- or left-handed. The table summarizes the class data. Gender Female Male Handedness Left 3 1 Right 18 6 A) Choose a student from the class at random. What is the probability the student is female given that they are right-handed? B) Are the events "female" and "right-handed" independent? Justify your answer. Prob & St