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  • Differences between group means/medians

    Dear All

    I have a panel data set (long) including 1245 firms over 10 years (2007-2016) with multiple firm characteristics (firm name, country, industry, year, DSO, DIO, DPO, CCC, leverage, growth, size, etc.) so every row/observation represents a firm-year.

    I would like to examine if the mean CCC is significantly different between the countries. How could I take into account that I have panel data(over 10 years) or is the only way to run -by year: anova CCC country- ?

    Also, I am trying to determine if the mean CCC per country changes significantly over the course of the ten years? I am unsure of how I can examine this for my entire dataset, the only method I could think of is to look at the countries separately with:
    bys country: anova CCC company year, repeated(year)

    Are there also methods to examine these two questions using the median CCC instead of the mean CCC?

    Thank you very much in advance for you helpful responses!

    Code:
    * Example generated by -dataex-. To install: ssc install dataex
    clear
    input long company int year double(CCC GROWTH LEV SIZE_LNTA ROA) long(country sector)
     1 2007    97.4272873157527   -.07094796166209166 .46760933903321433  3.211742830078779   .054203661076400275 6 7
     1 2008  149.99922356229743    -.6151534856863113  .3889114541023563 2.7380554508006867   -.03188464662875716 6 7
     1 2009   82.20915454225528     .4600768999979168  .3242220353238024  2.596491630822129    .04196804037005898 6 7
     1 2010    77.8854901541128    .06993466765472521 .24658254468980023 2.5883279706847095    .05432877672625297 6 7
     1 2011   47.38709857159552     .3297141183703392  .2570475901788419  2.762297448013138    .08866323128220635 6 7
     1 2012   73.12467489899241   .027809536194332254  .2925880063683011 2.6337201858101924     .1192287281089692 6 7
     1 2013  120.25850404365345    -.2451758743544866  .2729682879575822  2.469174642673046   -.02488018762108701 6 7
     1 2014   72.31341983708305    -.1088421865980785   .268977248564747 2.4939228240679068   -.04071869019774627 6 7
     1 2015  21.891916240400022    .42846451781462624  .7404329761644416  2.518656387078679    -.5275530286464022 6 7
     1 2016   9.900967620405766    -.1832128141642182  .9504402515723264  2.233072214902751   -.28968553459119506 6 7
     2 2007   -5.74156547075691     .2366080591092564  .5798280641706948  4.604379873773648    .01564235746239529 2 6
     2 2008 -1.4571604053639078  -.009165260527601816  .5510545970659748  4.453847171211826   -.04631385460171947 2 6
     2 2009   3.307125847037547   -.08950390381447816  .5225485188968336  4.360802998222255  .0004851889683350358 2 6
     2 2010  22.899390969687346    -.4847967620936008 .48041641559507176  4.356696006094587  -.018205361607200092 2 6
     2 2011  21.478866579368542    .36347405173781944 .16412512089455344  4.323854471869926   -.03708316220405676 2 6
     2 2012  30.457253685027155  -.062272661137785554 .14238141650422353  4.120012308970678   -.17267706302794023 2 6
     2 2013   47.33064783267083    -.3442358417377812 .17412569024454377  4.043840430048332    -.0852835480760803 2 6
     2 2014   46.88939305230288    .21237932992617828  .5044334515587082  4.450992839138604   -.04236279634123576 2 6
     2 2015    62.9719723183391  -.012978142076502715  .4818006665278067  4.341412951788585  -.009568319100187461 2 6
     2 2016  101.64495546989234   -.10750370736529914  .5767632254965435  4.561865946578819   .007215805852008103 2 6
     3 2007  28.648255813953483    -.6244541484716157 .11090966776956897 3.0939019973262343     -.368490232515977 2 5
     3 2012   82.13128876636803      4.58076923076923 .24956135824130454 3.3696035100709767    -.4547080882099976 2 5
     3 2013    82.4673735725938    .12657937054904667 .36277887602372216  2.873847085563867    -.5944648404405536 2 5
     3 2014 -15.495038979447205    .43862153344208804  .8627293424400697   2.70364049261351    -.6492567296102852 2 5
     4 2007    44.7822333344485    .19733223223119858  .6384142763445507   4.52810091428275   .032749810683725546 6 2
     4 2008  28.560925537404835    .10131198217676028  .7035054714137968 4.2901477565695245    .06362818505962337 6 2
     4 2009  17.218482646648027   -.16231278013157763   .783643201551085  4.330130802699381   .034430788933291816 6 2
     4 2010  23.635610738623377   -.09932149380532652  .7686911195100232  4.463212524829102   .039466812945542676 6 2
     4 2011  14.391438025202909    .18610817711179906    .82051493759947  4.469371631264115   -.02259004989209076 6 2
     4 2012   10.60220979004334    .11850125540296277  .7709241589207864  4.298650774631349    .07025572715308052 6 2
     4 2013   8.346814522560496    .10101402758078037   .692843107869584  4.182911569216697    .11783838989354026 6 2
     4 2014  1.5918643715924787     .4094408695109606  .8115481978543014  4.116164091458351    .21908359116540094 6 2
     4 2015   .9356116044853593     .3409360999985676  .6831202387846929  4.415134377600082     .2527620617454448 6 2
     4 2016  -.7712816117305792     .1595291019464831  .6767241379310345  4.457658719063974    .26984301966663726 6 2
     5 2007   121.2734392647858    .09466706841445573  .4012204074142043  4.567987612175217    .03418058359331981 6 6
     5 2008  134.95116492007963   -.12311208212570741 .40693256617520585  4.391206188396731   .031238762332119033 6 6
     5 2009  133.53572431864683   -.16022820409874902 .42903862528059494  4.019239533913847   -.14648966638284708 6 6
     5 2010   178.6698238467825    -.3773608780693818   .539206663292071 3.8908673616651317    -.2005430030831529 6 6
     5 2011  197.50183287580677   -.19240719291450026  .5007483134166834 3.8954709792824787    .04634938177799276 6 6
     5 2012   137.2090366941855    .09202291080859164  .7960059560304807    3.7159412536008   -.28005021751189807 6 6
     5 2013   97.35058500038596    .09946118281387034   .513358649978654  3.966065869705537    .05294025121901889 6 6
     5 2014   96.82241955185612     .0180945970144641  .4844854000411589 3.9684853076747304    .04234788374911396 6 6
     5 2015   96.74715906962086     .1859688316322326  .5162034770689679  4.581770011305192    .03286851196553703 6 6
     5 2016  115.43575854441406   -.05514028744995535   .468035221174386  4.563110046212338   .014927317251081087 6 6
     6 2007   35.54697128771626     .3985795227834969  .4209427476107342  4.017481516284286  -.012094814708158602 2 9
     6 2009  -35.55279330535605    14.594154164511123  .6357812248536093  5.777986632660106    .01776186290652042 2 9
     6 2010  20.931009276063726     .6451307910494801  .7669419240535195  5.429472813848555    -.2866477509439589 2 9
     6 2011    32.0772641856488   -.49295724944545277  .7963233818004532  4.937892543449571   -.16437953483036508 2 9
     6 2012  37.749402513298904    -.7420682661045766  .8414806557733613   4.29812858805602   -.06160789538076725 2 9
     6 2013 -1.7829230168034407    -.6054274920977565   .790648870981281 4.6748548181534435  .0036468097409925668 2 9
     6 2014   -5.74388400219901     .4216490816725282  .8158215146804753  5.336542391860967    .03578561356734827 2 9
     6 2015  -5.476007412664618     .7428532160527762  .7650993782720041  5.578770875774367   .020929494685472116 2 9
     6 2016  -36.03130983032944    .19446415897799868  .7522372247538264  5.652710208471697   .016508631425334052 2 9
     7 2007   48.66801533143904    -.2998443524827151  .3514264074728602 2.8627576640941443   -.07254060422452267 6 2
     7 2009    184.170338207606   -.24061352400842334 .37032666749472126 2.8569565980384404   -.04732331387405291 6 2
     7 2010  48.610117154501424     .4566744219493445 .38456275656176203  2.894136137548722   -.03383505411120792 6 2
     7 2011   62.50911360347707   -.09075605493867156  .1751327433628316  2.548561696124731   -.06530973451327408 6 2
     7 2012    65.5460195026056   -.23336869748571068 .20647287983218515  2.080444872567682   -.33008690440515476 6 2
     7 2013  39.918956158009294    .15261780095741764 .19912790697674493 1.8759843677063865   -.16170058139534868 6 2
     7 2014   35.49259665350056    1.9477504277268836  .3093346573982116  3.032139376521263   -.16317030784508385 6 2
     7 2015   91.19377776797154    .07265789461475995  .5414906663033114 2.2985423554057394   -1.0745333151655498 6 2
     7 2016   89.88190801264355  -.009971345171912232 1.2132193268186726  2.157046585189516    -.7254343105320299 6 2
     8 2007   75.05607005696163    -.0688541071194405 .31464280228619523  5.118735072028397    .13612074471095184 6 3
     8 2008   70.83959102338174   -.03935028755574109  .5042319380243098  5.357112300487695    .09135315014552328 6 3
     8 2009   62.66589571553435     .2073380640618123 .47615821211347503  5.400382974419964    .09354299026940269 6 3
     8 2010   69.57195783829798    .11424780094130697 .42273981817642203 5.4618963574437265    .11171070464055725 6 3
     8 2011   75.58187480158139   .023608061636401046  .3527643312101908  5.453110080415042    .14341910828025473 6 3
     8 2012   75.25199831033096   .051788220492579876  .3918766698628734  5.530234513691734     .1181681080628194 6 3
     8 2013   72.39280091324433    .09788631909124498  .3157611713991021  5.611030545238669    .12420550613997192 6 3
     8 2014   66.25874411404502     .1393810599676851  .3855101023384357   5.83090779142603     .1177657482246816 6 3
     8 2015   74.96131356533878  -.025460107710263684 .33048327137546524  5.868428878316495    .12750929368029723 6 3
     8 2016    80.8561174694199   -.11292334477354597  .3403483309143677  5.778661510287361    .12917271407837452 6 3
     9 2007   145.7276119402985    -.5942321557317952  .6697354961274294  8.830981510952498    .05392371766768961 3 9
     9 2008  30.905808992451597    1.1656005685856432  .6524625459764959  9.318925682389624    .03095003139858258 3 9
     9 2009   55.34808368820589   -.11371841155234658  .6975409836065574  9.409191230721348   .007213114754098361 3 9
     9 2010  55.979556364840235    .11849657470838734  .7065627357304501    9.3868953338758   .019696588718464504 3 9
     9 2011  55.017944535073426   .014732660155603377  .7450944265315523  9.292381082312392  -.010225702441271304 3 9
     9 2012    51.2013888888889   .057096247960848286  .7617413143574717   9.38806805975991    .01992465466722478 3 9
     9 2013   58.52114561027838   -.13518518518518519   .746503178928247  9.306559229716726   .006811989100817439 3 9
     9 2014   54.96237961476726   -.11063526052819414  .7504113035904384  9.243097936214355 -.0017419916771508758 3 9
     9 2015   41.90713269660637  -.012640449438202247  .7300275482093664   9.19023970026918 -.0058157330884603614 3 9
     9 2016  39.524347143137646    .03495224547856127  .7382214086135466   9.24753981296529   .022834569804412758 3 9
    10 2007   38.26833010062731    .08373317423304491  .9061618507478528  10.81161392655746   .018532268095758784 4 6
    10 2008  100.11366492492894 -.0009193182222745826  .9345944410998336 10.840117238445798   .019729748903333427 4 6
    10 2009   87.84921233360353 -.0014480970900393715  .8654502440181328  10.35332654771914   .027541585310814378 4 6
    10 2010   86.79993368382891   -.07028578498772482  .8777649607379385 10.439528393774182    .03724571061053441 4 6
    10 2011  42.025290968637364     .9411393700434169   .930834624413148 10.778698110731323   .022144904114726784 4 6
    10 2012   31.20495502182534     .3485647577295818  .9360851245577357 10.634974673867829    -.0364526452326683 4 6
    10 2013  34.053993366469825   -.08381633713647226  .9182314022344189  10.59576883331304   .027115344008122627 4 6
    10 2014   34.61340044368174    -.0084453753432086  .9228521033495432 10.579507266863608   .011790598522636975 4 6
    10 2015   34.02479758305691  -.045570866085297194  .9030321803156183 10.471066634825396   .028202149965130215 4 6
    10 2016  29.542087946125264   -.03953275012406396  .8926735249705557  10.41551043929666   .017852912567802023 4 6
    11 2007    69.9203078806221     .5029887375004641  .6805318138651472  2.052855614019718    .11775878442545099 6 6
    11 2008   58.47764042881351    .04753992138456384  .6311772315653303  2.261190826201738    .09133247089262611 6 6
    11 2009   49.81345843460397    .05998915593863629   .676912080057183 2.0724807236470806   -.09092208720514647 6 6
    11 2010   53.66814581719369   .013899030055557737  .5762817515973191 2.0495747570462837   .027894654823126124 6 6
    11 2011   45.95889745352021   .004523315865717586  .5261001517450686 2.0081444191792226    .04476479514415783 6 6
    11 2012  43.848252776959555     .0560149145403645  .4514276599138614  2.067957148526853  -.005104482373584267 6 6
    11 2013   41.20196693895602    .47596475685182427 .30821784110872513  2.891975775013006     .2772464051011775 6 6
    11 2014  44.605709692735005   .026502613974257037  .2851877303679647 3.0071954390651605   .018866745798713096 6 6
    end
    label values company company
    label def company 1 "21st Century Technology PLC", modify
    label def company 2 "3U Holding AG", modify
    label def company 3 "4Sc AG", modify
    label def company 4 "4imprint Group PLC", modify
    label def company 5 "600 Group PLC", modify
    label def company 6 "7C Solarparken AG", modify
    label def company 7 "7digital Group plc", modify
    label def company 8 "A.G.Barr PLC", modify
    label def company 9 "A2A SpA", modify
    label def company 10 "ACS Actividades de Construccion y Servicios SA", modify
    label def company 11 "APC Technology Group plc", modify
    label values country country
    label def country 2 "Germany", modify
    label def country 3 "Italy", modify
    label def country 4 "Spain", modify
    label def country 6 "United Kingdom", modify
    label values sector sector
    label def sector 2 "Consumer Cyclicals", modify
    label def sector 3 "Consumer Non-Cyclicals", modify
    label def sector 5 "Healthcare", modify
    label def sector 6 "Industrials", modify
    label def sector 7 "Technology", modify
    label def sector 9 "Utilities", modify

  • #2
    Dear Vivian,

    Possibly, this paper offers good advice to compare and examine median values between group categories:
    http://www.stata-journal.com/article...article=st0253

    Best,
    Eric
    http://publicationslist.org/eric.melse

    Comment

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