NBME 21 Answers ↦

nbme21/Block
3/Question#24
(52.9 *difficulty score*)

Diastolic blood pressures are obtained in two ...

Median of group Y: higher; Mode of group Y: higherπ,πΊ

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Diastolic blood pressures are obtained in two ...

Median of group Y: higher; Mode of group Y: higherπ,πΊ

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sahusema
Wow. I hate this. I only looked at the number of participants and completely ignored the Diastolic BP readings
+5

ma_rad
Everyone commented how to get the mode right. But there is an easier way to realize that the median in Y is higher without all the calculations. If you see, the last Diastolic BP in group X is 110 (as there are ZERO people with 120). While group Y has 8 people with 120 DBP. This automatically shifts the median to the higher side.
I got this wrong though at first I didn't pay attention to the "0" number at group X for 120 DBP
+9

brasel
I think there's another easy way to find the median without writing out every value. There are 100 total people in each group, so that means the median (if the DBPs are written in ascending order, which they are) is the 50th person.
Group X: 8 + 12 + 30 = 50, so median is 70
Group Y: 2 + 8 + 10 + 20 +10 = 50, so median is 90
+8

mangotango
I did it the way @brasel explained. The way @ma_rad did it could give the incorrect answer in some cases (e.g. Group X had 0 ppl with 120 BP but a ton of ppl for 110 BP etc. + Group Y had 10 ppl with 120 BP but basically none with 110 BP etc.). In this question that way worked but it's not always guaranteed since median doesn't sway with outliers, but mean does. // FA 2019 pg. 261
+

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fadila
median should be: 70 for group X ; 85 for group Y
median here is the avarage of Diastolic BP measured betweeen the 50 & 51 patients (since the number of patients in each group in even; Median= (n+1)/2 -> (100+1)/2= 50.5)
Group X = (70+70)/2 = 70
Group Y = (80+90)/2 = 85
+1

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rnyEveeo dtocenmme woh ot teg hte mdoe .itgrh uBt rethe si na esiear awy to lezeira atth eth mdaien ni Y is rigehh howutti all teh nliaucls.acto fI you e,se teh lsta ocDlaiist BP in gopru X is 101 (sa hrete rea ERZO ploepe ihwt 0.1)2 hWlei prguo Y has 8 eeplop htwi 102 PD.B hiTs claalmtoaiytu isshtf eth nmdiea to eht ihgreh .ised

I ogt isht wongr hghuot ta tsrif I dt'din pay ennittaot to eth ""0 enmbur ta pgoru X rfo 021 DPB

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r-0ezg0ld4i-9j2-.-lFeRnS1781u-pe1

syror rof hte ,nkapin hope ttha lilw ehpl eeomnos

yb_26
[https://www.reddit.com/r/usmlestep1/comments/c96406/explanation_for_question_from_nbme21/]
+2

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acn oennya xaeinpl h?sti i konw niemda rfo y si igrhhe by iuactlalonc btu x sah wot dosme os who moec y sah hiegrh o?dem

hungrybox
Just checking in so I could feel smart about getting this right despite bombing the rest of the test lmao
+4

nala_ula
The median can be known by first assembling the numbers in order from least to greater.
If it's an uneven number set, the number in the middle is the median (for example: 4, 10, 12, 20, 27 = median is 12 since this is the number in the middle); if the numbers are even then you have to take the two values in the middle, add them up and divide them by 2 [for example: 4, 10, 12, 12, 20, 27 = (12+12)/2 = 12].
Page 261 on FA 2019 explains it as well. Not sure if I explained it well... good luck on the test, people!
+

dubin johnson
Can someone please explain how the mode for Y than X. Not sure how we got the values above. Thanks!
+

usmile1
Median would be the BP value that the person in the 50th percentile of each group would have.
So for group X, to find the 50th percent value, I added 8 + 12 + 32 = 52, which is right above 50, so the median would be 70 mmHg for group X.
Doing the same thing for group Y, 2+8+10+20+ 18 = 58; the 50th percentile would fall in group that had a BP of 90 mmHg. which makes the median higher for group Y.
hope that isn't wrong, and helps someone!
+4

poisonivy
I did it the same way! not pretty sure if it is the right way to do it, but it gave me the right answer!
+

submitted by amarousis(23), 2019-06-23T20:54:51Z

so orf hsit oen ouy aehv to oolk at het soicilatd lobdo rsupesre nad tha'st hte aeuvsl or'yeu ppsuesdo to era.d tno hte ubensrm in hte ml.sconu Leki rguop 'sX medo si 07 eeaubcs ti sha atth alevu 23 .emsit purog sy' dmeo si 08 bueaecs ti apasrpe 20 m.esti fro e,mdnia oyu wluod have ot iwert teh istoailcd mnureb 025-10 hwo eerv anmy msite ti aseprap dan tneh nifd teh ldi.emd iytrkc neoisq.ut