# Statistics- stem leaf qWatch

#1
Can someone please clear my doubts?

At first I thought interpolation should be used. Is that possible over here? Can interpolation ever be used in stem leaf diagrams to find quartiles?

If I use 31 (i.e n+1) instead of 30 (n) is that fine or would it lead to the wrong value in other qs like this one?

1 week ago
#2
No, you don't need to use interpolation in stem and leaf diagrams.

If you use 31 instead of 30,
Q2(median)=31/2=15.5th term so this works for finding out the median.
BUT
Q1(lower quartile)=31/4=7.75th term and Q3(upper quartile)=(3x31)/4=23.25th term and so it doesn't work for finding out upper and lower quartiles.

However, you can use 31 as detailed in this video but the method is a little different. https://www.youtube.com/watch?v=JK0zHW_ThjY

Hope this helps!
Last edited by lionpunkgirl; 1 week ago
1
#3
Thank you soo much!
(Original post by lionpunkgirl)
If you use 31 instead of 30,
Q2(median)=31/2=15.5th term so this works for finding out the median.
BUT
Q1(lower quartile)=31/4=7.75th term and Q3(upper quartile)=(3x31)/4=23.25th term and so it doesn't work for finding out upper and lower quartiles.
But in the example they just rounded 7.5 and 22.5 to get 8 and 23 so why can't we just use this and round off the values to 8 and 23 with this too? Would it make a difference in other qs like this? It also worked with example in the video
1 week ago
#4
Honestly you probs could but I would just be careful and do the counting method at least to check if you're right for accuracy's sake in exams when trying to find quartiles. It doesn't make too much difference in time so do what you're comfortable with.
0
#5
(Original post by lionpunkgirl)
Honestly you probs could but I would just be careful and do the counting method at least to check if you're right for accuracy's sake in exams when trying to find quartiles. It doesn't make too much difference in time so do what you're comfortable with.
You're right, thanks!
1 week ago
#6
No probs
0
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