Exam grades: Scores on a stats final in a large class were normally distributed with a mean of 75 and a standard deviation of 8. A) What proportion of the scores were above 90? B) What porportion of the scores were below 65? C) What is the probability that a randomly chosen score is between 70 and 80? *show by Tables and Technology
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For 90: z = (90 - 75) / 8 = 15 / 8 = 1.875 For 65: z = (65 - 75) / 8 = -10 / 8 = -1.25 For 70: z = (70 - 75) / 8 = -5 / 8 = -0.625 For 80: z = (80 - 75) / 8 = 5 / 8 = 0.625 Now, we can use the z-table or technology to find the proportions. A) The proportion Show more…
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