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# Problem in statistics...pls help

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 Abheer student [ Scorecard : 187] Posted On 03 June 2012 at 02:38 A population comprises 5 members. The number of all possible samples of size 2 that can be drawn from it with replacement is a) 100 b) 15 c) 125 d) 25 pls give the reason too as i already know the answer...thnx in advance :) C.A. abhishek ManagementConsultant@KPMG [ Scorecard : 511] Posted On 03 June 2012 at 02:46 Hey your problem is tooo complex in front of mine...i hope you can help in this..... here's my question... how to compute pooled variance?? If we are given N (Population Size) Mean (X) and Variance for say 2 groups how can we compute the combined/pooled variance??????? intermediate(ipc)course no [ Scorecard : 1446] Posted On 03 June 2012 at 06:10 sample size with replacement = N^n = 5^2 = 25 priya Student [ Scorecard : 64] Posted On 03 June 2012 at 09:32 Lets say we have 5 items - Sample Space = [B1, B2, B3, B4, B5] From this we are selecting 2 with replacement. Lets say we are selecting B1 first. Now the sample space would be [B2,B3,B4,B5]. B1 in our hand. We are selecting with replacement. Hence we keep the item B1 back into the sample space. Now the sample space is [B1, B2, B3, B4, B5]. Now select the 2nd item which could be either B1, or B2 or B3 or B4 or B5. ie the pair of items selected would be (B1,B1) , (B1,B2) , (B1,B3) , (B1,B4) , (B1,B5) - 5 ways of selecting. Now the same could be applied with selecting B2 as the first item.  (B2,B1) , (B2,B2) , (B2,B3) , (B2,B4) , (B2,B5) - 5 ways of selecting. Likewise for B3,B4 and B5. (B3,B1) , (B3,B2) , (B3,B3) , (B3,B4) , (B3,B5) - 5 ways of selecting. (B4,B1) , (B4,B2) , (B4,B3) , (B4,B4) , (B4,B5) - 5 ways of selecting. (B5,B1) , (B5,B2) , (B5,B3) , (B5,B4) , (B5,B5) - 5 ways of selecting. Thus the total ways of selecting 2 items from 5 items with replacement is 25. It is generally given by the formula N^n. N-  Total size  and n - sample size. Hope the explanation is clear. Thanks.

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