NBME 21 Median of group Y: higher; Mode of group Y: higher (NBME Answers)

Retired NBME 21 Answers

nbme21/Block 3/Question#24 (reveal difficulty score)
Diastolic blood pressures are obtained in two ...
Median of group Y: higher; Mode of group Y: higher 🔍 / 📺 / 🌳 / 📖
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submitted by ∗amarousis(27)

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so for this one you have to look at the diastolic blood pressure and that's the values you're supposed to read. not the numbers in the columns. Like group X's mode is 70 because it has that value 32 times. group y's mode is 80 because it appears 20 times. for median, you would have to write the diastolic number 50-120 how ever many times it appears and then find the middle. tricky question.

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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 +11

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 +12

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 +2

unknown001 for median write down every value ? i reeeally hope you were joking, the data is already arranged from least to greatest, which is a criteria for determining mean. now add up till you reach 50, and correlate it with value of diastolic blood pressure and BOOM, its that easy +

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submitted by ∗yb_26(316)

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

sorry for the napkin, hope that will help someone

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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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submitted by ma_rad(13)

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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

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+1 upvote downvote
submitted by ∗yb_26(316)

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FullSizeRender-04-07-19-11-28.jpg

sorry for the napkin, hope that will help someone

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yb_26 tried to attach photo, sorry for that( +

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

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submitted by hajj(0)

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can anyone explain this? i know median for y is higher by calculation but x has two modes so how come y has higher mode?

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lispectedwumbologist The mode in X is 32 and the mode in Y is 80 +

lispectedwumbologist The mode in X is 70 and the mode in Y is 80* +1

hajj Thank you! +

hungrybox Just checking in so I could feel smart about getting this right despite bombing the rest of the test lmao +5

usmleuser007 can someone please explain the median in this +

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! +

dubin johnson I mean how is the mode for Y greater than mode for x? +1

sgarzon15 Mode is the one that repeats the most once you list them in order +

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! +

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