NBME 21 Answers ↦
Wow. I hate this. I only looked at the number of participants and completely ignored the Diastolic BP readings
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
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
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
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
tried to attach photo, sorry for that(
Just checking in so I could feel smart about getting this right despite bombing the rest of the test lmao
can someone please explain the median in this
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!
Can someone please explain how the mode for Y than X. Not sure how we got the values above. Thanks!
I mean how is the mode for Y greater than mode for x?
Mode is the one that repeats the most once you list them in order
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!
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!