freezer Posted September 5, 2007 Share Posted September 5, 2007 There are these 8 numbers in a set 9.4,9.9,9.9,9.9,10.0,10.2,10.2,10.5 The mean and standard deviation of the 8 numbers are 10.0 and 0.3 respectively, what percent of the 8 numbers are within 1 standard deviation of the mean? a) 90% b) 85% c) 80% d) 75% e) 70%Need a detailed solution: Thanks Quote Link to comment Share on other sites More sharing options...
krishna_k1 Posted September 5, 2007 Share Posted September 5, 2007 1 standard deviation in this case is 9.7 to 10.3 six numbers are within this range so the answer is 6/8 * 100 = 75% Quote Link to comment Share on other sites More sharing options...
aru4912 Posted September 9, 2007 Share Posted September 9, 2007 Agree; three 9.9's ,10.0 & two 10.2's are within 1 SD of the mean (10.0) => 6/8 * 100 = 75% Quote Link to comment Share on other sites More sharing options...
karta Posted September 18, 2007 Share Posted September 18, 2007 Can anyone please explain the solution above in detail. What does 1 standard deviation mean ? Quote Link to comment Share on other sites More sharing options...
jsackmann Posted September 18, 2007 Share Posted September 18, 2007 The question says "The mean and standard deviation of the 8 numbers are 10.0 and 0.3 respectively" so: mean = 10 sd = 0.3 "one standard deviation" = 1*(sd) = 0.3. two standard deviations would be 2*(sd) = 0.6, etc. A number that is within SD away from the mean could be greater or less than the mean -- in this case, it could be either of the following: greater than 10 - 0.3 = 9.7 less than 10 + 0.3 = 10.3 --- GMAT Hacks: Improve Your GMAT Score! Quote Link to comment Share on other sites More sharing options...
sharma1617 Posted August 6, 2010 Share Posted August 6, 2010 The fourth grade at school X is made up of 300 students who have a total weight of 21,600 pounds. If the weight of these four graders has a normal distribution and standard deviation equals 12 pounds, approximately what percentage of the fourth graders weighs more than 84 pounds? a 12% b 16% c 36% d 48% e 60% need detailed explanation,,and also want to know what are bell curve questions and how it will relate with standard deviaion. thanks Quote Link to comment Share on other sites More sharing options...
ramgorur Posted August 7, 2010 Share Posted August 7, 2010 here μ = 72 μ + 1.σ = 72 + 12 = 84 [ATTACH]5758[/ATTACH] % of students above 84 = 13.6% + 2.1% + 0.1% = 14.8% ≈ 15% Quote Link to comment Share on other sites More sharing options...
matt01752 Posted August 9, 2010 Share Posted August 9, 2010 Where did you get this question? My believe is that GMAT will not be asking questions like this.... Mean = 21600/300 = 72 Mean + 1sigma (std dev) = 72 + 12 = 84 +/- 1 covers 68.2% (34.1% + 34.1%) of the normal distribution. Therefore, remain distribution of data 100% - 68.2% = 31.8%. Since we care only about data points above 84 lbs => 31.8 / 2 = 15.9% = 16% What's the answer? +Matt Quote Link to comment Share on other sites More sharing options...
sharma1617 Posted August 13, 2010 Share Posted August 13, 2010 This question is not from GMAT preparation. This is from cracking the GRE from princeton review. Since i got stuck by this question that why asked it, and yes the correct answer is 16% Quote Link to comment Share on other sites More sharing options...
sharma1617 Posted August 13, 2010 Share Posted August 13, 2010 PERMUTATION AND COMBINATION A teacher prepares a test. She gives 5 objective type question out of which 4 have to be answered. Find the total ways in which they can be answered if the first 2 questions have 3 choice and last 3 have 4 choice. help me with this question,,is there any specific formula applied in thes type of questions??? Quote Link to comment Share on other sites More sharing options...
minnsy229 Posted June 26, 2012 Share Posted June 26, 2012 http://www.www.urch.com/forums/webkit-fake-url://350ECB12-95DF-408F-9FA2-B29AFD7EC8BD/imagepng Quote Link to comment Share on other sites More sharing options...
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