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Warm-up 2.5 Day 2 1)An incoming freshman took her college’s placement exams in French and mathematics. In French, she scored 82 and in math, 86. The overall results on the French exam had a mean of 72 and a standard deviation of 8, while the mean math score was 68 with a standard deviation of 12. On which exam did she do better compared with the other freshmen? Warm-up Day 2 2) Two companies market new batteries targeted at owners of personal music players. DuraTunes claims a mean battery life of 11 hours, while RockReady advertises 12 hours. a) Explain why you would also like to know the standard deviations of the battery lifespans before deciding which brand to buy. b) Suppose those standard deviations are 2 hours for DuraTunes and 1.5 hours for RockReady. You are headed for 8 hours at the beach. Which battery is most likely to last all day? Explain. c) If your beach trip is all weekend, and you probably will havethe music on for 16 hours, which battery is most likely to last? Explain. Mooseburger vs.McTofu 3)M-burgers’s weekly payroll number are mostly higher than McTofu. McTofu has an outlier that is out of place. McTofu vs. Mooseburger 4) On average Mooseburger pays the higher salaries. 5) The mean salary is misleading for McTofu because it has an outlier which will make the mean payroll considerably higher. 6) Mooseburger has consistently higher payrolls, McTofu has one high payroll number which may be a manager. This McTofu’s numbers misleading. Student of the Day! Block 4 Student of the Day! Block 5 Student of the Day! Block 6 Z-score Z-scores (for normal distribution) describe how many standard deviations (σ) a piece of data is from the x mean(μ). z The z-score can also be used to find the proportion of values above or below the z-score using normalcdf (z-score, upper or lower bound) invNorm is for finding the z-score when the percentile, mean and standard deviation is given. invNorm(percentile,mean, standard deviation) Practice with z-scores and finding proportions. 1) A distribution of quiz scores has a mean of 35 and an standard deviations of of 4. Sara received a 40. a) What is her z-score? b) What is her percentile rank compared to the rest of the class? 2) In a normal distribution with mean 25 and standard deviation 7, what proportion of the data are less than 20? Multiple Choice Practice • Answer 1 – 10 by yourself. • Once everyone at your table is done, discuss your answers. • Submit your group answers on a separate piece of paper to be graded for accuracy. H.W. E #63- 65. Draw the bell curve and label standard deviations for each of the problems.