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  • 1.  Merging to independent samples

    Posted 06-19-2017 08:49
    Dear colleagues any proposals on how to merge two samples: one designed as stratified cluster sampling and the other as simple random sampling of individual units?
     Yiannis C. Bassiakos Associate Professor, DoE, UoA 1 Sofokleous street, 15509, Athens, GREECE tel. +30210.368.9491 mob. +30697.419.2133 Skype: yiannis.c.bassiakos


  • 2.  RE: Merging to independent samples

    Posted 06-20-2017 03:19
    were the two samples drawn from the same population at the same point in time?

    www.twobluecats.com
    www.datastatisticsonline.com
    www.twobluecats.be




  • 3.  RE: Merging to independent samples

    Posted 06-20-2017 08:49

    How, or if, you merge your two samples depends on what your purpose is for doing the merging.  I think we need to know more about the data and your goal to answer your question.  The previous question about the timing of the sampling is also useful to know.

     

    Bill Bentley

     

     






  • 4.  RE: Merging to independent samples

    Posted 06-20-2017 13:53
    The two samples will be drawn concurrently (let's say from inde[endent populations) and one of the objectives would be to use regression method to compare the two populations

    ------------------------------
    Yiannis Bassiakos
    Associate Professor
    University Of Athens, Economics Department
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  • 5.  RE: Merging to independent samples

    Posted 06-20-2017 14:59
    one possibility is not to merge them at all, but to do the appropriate analyses for each and then use metaanalysis.

    --
    Ellen Hertzmark

    (617) 432-1200 (1635 tremont st--usually wednesdays 1:30-5)



    please call before coming to my office.

    (617) 734-6245 (home -  any time except sundown friday to 1 hour after sundown saturday))





  • 6.  RE: Merging to independent samples

    Posted 06-21-2017 08:43
    Based on your experimental conditions (one stratified sample and the other random independent sample), I am not sure there is any "appropriate" method of merging.  Meta analysis or Fisher's combining evidence require the samples whose outcome evidence (such as probabilities) one is combining should come from experiments/samples from equivalent experimental and sampling conditions.  In my opinion, the only thing that could be done with these two differently conducted experiments is to use the evidence from them to design a good experiment.  The variance estimates from the two samples along with their expected values could be used to compute approximate sample sizes for the new design.

    Ajit K. Thakur, Ph.D.
    Retired Statistician

    ------------------------------
    Ajit Thakur
    Associate Director
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  • 7.  RE: Merging to independent samples

    Posted 06-22-2017 09:17
    It seems that you have a finite population and two independently drawn samples. Maybe I am missing something, but here is what I would do.

    1. Separately estimate any quantity of interest, say the mean or total, along with estimated variances.

    2. Since both estimators are estimating the same quantity, use the the weighted average of both with weights given by the inverse of the estimated variances.

    3. You could test that they are estimating the same thing by subtracting the estimators and dividing by the square root of the sum of estimated variances. Compare to a standard normal.

    ------------------------------
    Dennis Boos
    Professor
    North Carolina State University
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  • 8.  RE: Merging to independent samples

    Posted 06-23-2017 10:42
    I agree with this answer, but note that it assumes the samples are large enough for the two variances to be well estimated. If not, step 3. should be replaced - perhaps by a permutation test of some sort.

    Robert

    Robert C. Elston,                                                            
    Distinguished University Professor Emeritus    Email:  robert.elston@cwru.edu                         
    Case Western Reserve University                   Website: http://darwin.cwru.edu/rce/  
            
    3000 Galloway Ridge, Apt G301                         Phone: (001) 919-542-0841
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  • 9.  RE: Merging to independent samples

    Posted 06-26-2017 00:52
    i would enjoy to have a little more information, if you can share:

    0 = say that population a is the one with simple random sample & pop b is the stratified one
    1 = what are the two population sizes, Na & Nb ?
    2 = what are the two sample sizes, na & nb ?
    3 = what was the stratified strategy and what was the simple random strategy adopted?
    4 = are the variables upon which the stratification occured also present in pop b?

    on of my research focuses is nonparametric, kolmogoroff-smirnoff enhancements. i am thinking that this sort of approach might enable no assumptions regarding parameters, especially variances. before going further, though, the answers to the above two questions seem quite important, and there seem to be many creative and valid strategies that could be embraced.

    regression seems interesting, too, and might benefit from weighting or other modifications.



    www.twobluecats.com
    www.datastatisticsonline.com
    www.twobluecats.be




  • 10.  RE: Merging to independent samples

    Posted 06-27-2017 09:45
    Dear colleagues, here is some more information as some of you requested:
    1. The two populations are of sizes 4,000,000 and 220,000
    2. the samples are 2000 and 500 respectively
    3. The first sample is three stage stratified cluster sampling (pps) of clusters (city blocks) with unequal sizes with optimal allocation into the strata and a fixed number (b) of observations (households) from each cluster.
    4. the second sample is stratified random sample of households with the same stratification variables as the first.
    5. One of the objectives is to run a logistic regression to estimate the relation of the characteristic defining the second population to a set of independent variables present in both samples. Say for example we want to model the probability of belonging to the second sample as a function of household income and size.
    --  ************************************ ?????????????? ??. ??????????????????, ?????????????????????? ??????????????????, ??????, ???????? ???????????????????? 1, ?????????????????? 6???? ????????????, ?????????????? 611, ??????. 210.368.9491  Yiannis C. Bassiakos Associate Professor, DoE, UoA 1 Sofokleous street, 15509, Athens, GREECE tel. +30210.368.9491 mob. +30697.419.2133 Skype: yiannis.c.bassiakos