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 Advanced Statistics Advanced Probability and Statistics Math Forum

 February 27th, 2016, 06:16 PM #1 Newbie   Joined: Feb 2016 From: Colorado Posts: 28 Thanks: 0 Stats practice question I have no idea where to even begin The mean grade on a statistics quiz is 8 with a standard deviation of 0.5. What percent of the scores will be higher than 9? Assume the data is symmetrical. February 27th, 2016, 06:24 PM #2 Senior Member   Joined: Dec 2012 From: Hong Kong Posts: 853 Thanks: 311 Math Focus: Stochastic processes, statistical inference, data mining, computational linguistics Can you assume the distribution is normal? If so, let X be the grade somebody gets on the test. $\displaystyle X \sim N(\mu = 8, \sigma = 0.5)$. $\displaystyle P(X > 9) = P(\frac{X - \mu}{\sigma} > \frac{9 - 8}{0.5}) = P(Z > 2) \approx 2.5\%$ (the exact answer will depend on the statistical table that your teacher gave you, but if you don't have a table, $\displaystyle 0.5 - \frac{0.95}{2} = 0.025$ is what you should answer). Last edited by 123qwerty; February 27th, 2016 at 06:27 PM. Reason: Clarify Tags practice, question, stats Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post vascosca Linear Algebra 2 February 15th, 2013 12:47 PM jackinda Algebra 2 January 18th, 2011 10:11 AM pudro Algebra 0 November 10th, 2008 08:12 PM hanahou Complex Analysis 0 November 13th, 2007 09:05 AM hanahou Complex Analysis 0 November 13th, 2007 09:03 AM

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