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 Probability and Statistics Basic Probability and Statistics Math Forum

 June 10th, 2015, 03:59 PM #1 Newbie   Joined: Jun 2015 From: Kiribati Posts: 5 Thanks: 0 Math Focus: Statistics Expected Total value Could anyone check my working out Two coins are selected at random from a wallet containing four 5 cent pieces, one 10 cent piece, three 20 cent pieces and two 50 cent pieces. What is the expected total value of the two coins? expected value = mean = ∑(x).P(x) But before using the formula you should created your Probability distribution table: cents...........5c.....10c....20c.....50c value of x......4......1.......3........2 P(x=x)..........2/5...1/10...3/10...1/5 Probability Distribution( from the table above) X........... 1.... 2..... 3..... 4 P(X=x)...0.1.. 0.2... 0.3... 0.4 By using the formula(∑(x).P(x)) all x values were multiplied by its probability and then add them together. = 3 I dont know if I do the right thing because and if I do some mistakes I would like to learn from it. June 11th, 2015, 07:46 AM #2 Senior Member   Joined: Mar 2011 From: Chicago, IL Posts: 214 Thanks: 77 \begin{matrix} Outcome\ x_i & 10¢ & 15¢ & 25¢ & 30¢ & 40¢ & 55¢ & 60¢ & 70¢ & $1 \\ Probability\ p_i & \frac{\binom{4}{2}}{\binom{10}{2}} & \frac{4\cdot 1}{\binom{10}{2}} & \frac{4\cdot 3}{\binom{10}{2}} & \frac{1\cdot 3}{\binom{10}{2}} & \frac{\binom{3}{2}}{\binom{10}{2}} & \frac{4\cdot 2}{\binom{10}{2}} & \frac{1\cdot 2}{\binom{10}{2}} & \frac{3\cdot 2}{\binom{10}{2}} & \frac{\binom{2}{2}}{\binom{10}{2}} \end{matrix}$\displaystyle E[X]=\sum_{i=1}^9 x_i\cdot p_i=0.38\$ Tags expected, total 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 sensational Probability and Statistics 1 June 10th, 2015 05:21 PM panky Calculus 2 May 27th, 2014 08:31 PM AamirAli Algebra 5 March 4th, 2013 01:39 AM fc_groningen Advanced Statistics 0 May 7th, 2011 04:52 AM MathematicallyObtuse Algebra 3 February 8th, 2011 01:41 AM

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