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NBME 21 Answers

nbme21/Block 4/Question#40 (reveal difficulty score)
A study is conducted to assess the normal ...
500 Men from a list of patients scheduled to be examined by a urologist 🔍 / 📺 / 🌳

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submitted by its_raining_jimbos(26),
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uOr titlel eifdrn has a sPavuirvor et,niiocfn wichh fcients oeydtrhri ru,rsreopsc naugsic nutirroitnpe of httrreyyceo cnpoi.rtoud sTih is eth eams way ti sauecs hrdpsyo tlisefa ni orunbn ebasib adn saitpacl maeina in icskel ,lcle .cte

submitted by seagull(1746),
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iixgnnEam natteip from a rgotilsuo mispeil kersBon asBi hichw odwlu ekws hte poltnpioua eamn of rumes euar nnteogir yaaw ofrm het eurt uectraca .amen ,Tneh ziealre nipceoris si dtedneepn no istatlatcsi erw"P"o hcwih is criedesan eadbs on the eszi fo teh upnapotlio fo teh .tdusy rci(anedes incoisrpe = ceneadsir sialatistct rfr,ehTeeo na secranei in nopalpoiut fo a esaidb urogp hwti deal to uiraccycan iwht ihgh iners.cpio

forerofore  to add up, the urologist himself doesn't add or remove accuracy (since this is a blood test), what decreases the accuracy is the fact that in order to be sent to a urologist you probably are sick in the first place (selection bias), so your urea nitrogen is likely to be altered. +25  
sharpscontainer  I thought of precision as more of a function of variance. Variance will decrease with a greater sample size. Had a hard time because I was thinking about those 4 darn targets (wouldn't 500 darts look more spread out than 10? but no, the variance will be better) that have been in my textbooks since 7th grade and for the first time I was asked a question about this concept only to discover that I didn't have it down as well as I assumed. +1  
peridot  @sharpscontainer I feel you, I thought the exact same thing. Looked into it a bit and I think it has something to do with the way standard error or standard deviation or something like that is calculated, but I'm still confused and too tired to dig further. Also, wanted to mention that this NBME has a similar question but instead it's about the 95% confidence interval - maybe that'll help you understand the precision thing better since the 95% confidence interval narrows with a larger sample size? So it's kinda tied to precision? +  

submitted by usmleuser007(435),
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1. elxmEpa of utearciacn ubt gylihh csereip 
    a. 500 naspetti eisgen a luarpriatc ocrdot rof a trrapulaci 
nesill2s. Expamel fo uraceact tub micepr
esi    .a 01 ptsainet orudegn a ercesgnin ta a laml .
3 tBho rAcuceta and rpeecis 
    a. 005 nspttiea (hghi p)iscornei nugored a rceginnse (gihh ccyucara ~ on siab ro emitscsy rre)r

submitted by drdoom(1045),
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cAacyrcu saemn teh atad ipnsto aer ,erddpssei utb wneh uoy kate hte nema fo oseth psti,on ttah name m“sel(pa ”mna)e si nayber eht lupnooipta eman e“tru( mn)”.ae aDta ptnsio rea “reom ier”psce fi eht oipdseisnr oscras adta nistpo si elamlrs anht some rheto ste fo taad siptno (teiocn woh itsh si a rnmicoopsa dna not an euabs”o“tl tnts;aete)m ipcroensi yass ghotnin ubtoa ohw cleso hte ageaver of hte dtaa npsito aer to hte er“tu .m”nea

pKee in midn atht ccycaura dna epnoriics rae itarevel reop;sstidrc you ca’tn ysa oao-sns-d“ is ;”espriec no, oyu cna lnyo say s“uasunh-h-dcc is orem ceerspi atnh sado”on-s- or ao“sd-nso- is moer rectuaca htan d.huuch-sa”nc-s oS, ni hits sea,c we acn nefir ttha BEMN codnsiser em“n ta eth uir”tloosg ot aevh NsBU ahtt rea leocsr ot ache ehtro (roem sle;teurdc orme se;ciper sesl eressdipd) hant hte BsUN fo “nem at al”m.l

e’eHrs a eicn egima:

submitted by cuthbertallg0od(13),
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iuiDssgcns noipcsier nloy saemk enses fi ethy eewr ot mspela "X # ianpes"tt mepulitl esmit adn ese owh csloe the dereffitn sermtnaeues'm ltsrsue rwee to heac otreh. ehT uacalt zise fo het epmals lst'hduo ceffta pnisirc,oe tub hetarr ti shludo sutj ftfeac cycauacr chi(hw si dcdereu by het ieasbd napiloputo ta teh )gols.uriot Shm

submitted by ali_hassan(3),
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How edos 500 nem ihtw auirosv culoigloar ncsionidot leutrs in a ireceps ?teitemsa 'odWlunt teh evriayt fo uasevl ude to suovair erseged of snelsil drecue cneripois adn ceuas a ewdir ieayrtv?

eayMb I eouhtrhgtov it

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