Median, Quartiles and interquartile range : ExamSolutions
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- Опубликовано: 22 окт 2012
- Median quartiles and interquartile range.
Finding the median, quartiles and interquartile range for a set of discrete data can often cause confusion. The position of the median for odd and even sets of discrete observations is discussed in the video.
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THANK YOU SIR!!!!! THIS IS THE BEST VIDEO I'VE SEEN FOR UNDERSTANDING THIS SIMPLE YET OVER-COMPLICATED PROCESS!! YOU SIR, DESERVE A MEDAL. MOST COLLEGE INSTRUCTORS CANT EXPLAIN IT THIS SIMPLY AND EFFECTIVELY.
Oh my! You just answered all the questions I had! Thank you SO much! I watched 10 other videos and this one is the best by far!
Thanks that was very helpful.
Thanks! Surprisingly, ETS doesn't mention these in their Official Guide to the GRE. This helped me recall what I'd learnt in AS.
Came across multiple videos that got this simple thing wrong. I trust your videos man.
In the first exemple it would be (6+1)/2=3.5 and in the second exemple it would be (6.5+1)/2=3.75
This was very helpful. Thank you very much.
Yesterday,I watched and listened how to calculate the median,SD and Q1,Q3, and IQR,so happy with my exam today morning......thank you Sir, my best tutor!
Thank you, my best supporter. Best wishes.
Agreed, your explanation made it soo easy thank you very much!!!!!
very useful especially in finding odd and even. clarity at its best
crystal clear explaination !!🥰👍👍👍👍 1 million like 😁😄
10 years later still helping out
This is great material for learning Statistics step by step in the comfort of your home garden.
OH MY GOSH!!!! THANK YOU 🥺
At the moment these are in specific worked solutions to some of the exam questions.
great video god bless you
and you
This hepls me a lot
very helpful .thanks
You're welcome.
Thanks a lot sir.
Thank you so very much
Very helpful video
Very helpful
You sir are a hero. I hope though there is no other method to get a different answer, and i am followin the one which is not asked :(
Excellent video. Beautifully explained. In the example with an odd number of values, you effectively discarded.the median value before calculating the lower and upper quartiles. Why are you allowed to do this?
I have enjoyed the teachings of quartiles but the part which is tricky is the percentile. If you can explain that again i will be glad. THANK YOU
Thanks a lot! Very clear explanation!
You're welcome. Pleased to hear it helped.
thank you so much because my class is so noisy so I can't hear the teacher, thanks
LEGO 7163 Thank you for using.
Quick question, Ive just started doing S1 and in my Jan exams when I did C1/2/3, majority of the books questions were pointless and what you needed to know was the basics and their application styles in exam questions.
Obviously you shouldnt rely on just one teaching method but would you say that your videos for the books give a fairly complete picture of the important stuff or is it only there to supplement the book?
very good i was able to use it for my demo teaching
+Biada Gallito Thank you and good luck with the teaching.
Very good, thank you!
Good to have your support, thanks.
Thank you this was really helpful
That's good. Thanks for watching.
It is to supplement the book
Thank you
You're welcome
It would be Q1, 12 - Q2, 16 - Q3, 18 and Q1, 5 - Q2, 10,5 - Q3, 15,75.
Um, I'm doing a 'problem' at the moment that has a median position of 10.5 and I see that on here (the right, even side) you've had 6.5 and made it just 6 for the lower quartile range equation, so do you ever round up/down, or do you just use a full number, whatever's in front of the decimal place, for the Q1 equation?...If you know what I mean?
No. If the middle position for the median is 10.5 then you have a list of 10 values to the left of this. So the middle position of this list will be (10+1)/2 which is 5.5. So take the mean of the 5th and 6th values to get the lower quartile.
Thankyou :')
if in a continuous series we find position of median 60 and 2 of the marks are 50-60 and 60-70,then in which Mark should be taken to calculate md?
perfect
Thx
Why did you add 1 in finding them?
I think the mistake would be when u try to get the low and upper quartile u have to count the number in the middle as well and not just the number on the right or left of it.
lol you're wrong
Thank You
You are welcome
do you always add 1 then divide by which quartile it is.
Thank you so so much!! This really helped me, I was so confused!!
No problem, pleased to see it helped.
Does anything change when your using different type of data, like discrete data and continuous data ?
Nathan Faulkner Yes but it is best if you watch this www.examsolutions.net/maths-revision/statistics/representing-data/grouped-frequency/median/estimating/tutorial-1.php
XD
Last test was for quadratics and I'm in maths advance class. The average class score that we got on the test was 40%, I got above average with a score of 44% XD
And we got mid year EXAMS tomorrow with statistics in it as well!!! XD
Help please, I'm not sure why but my teacher taught us like this: For example in the 2nd set of values to find Q3, we would do 3/4*n so, 3/4*12 = 9th value, then we count in the table till the 9th value, which is 15 so Q3 = 15, is this wrong? why did she teach it like this?
Wow!!!!!!!
I`m a little confused as - since you say - trying to find the mid number of a large set of values is not so easy as trying to find the mid number of a dozen or so values. Eg, there may be 999,000 values. Adding 1 and dividing by 2 would mean that we are looking for the value that occupies the position 500,000. So we have to count each value, one by one, up to half a million. What am I not getting ?
Is it possible to discount the thousands ? And then the hundreds ?
If there were 999,000 values, adding 1 and dividing by 2 would give 499500.5 so you would have to find the mean of the 499500th and 499501th value. As to finding which value this was you would have the data set input into a computer which would then with the right software easily work out the median. This is very unlikely to be a question in an exam.
U saved my life-
Feels good. Best wishes.
Ser what if I have 2 the same numbers? am I gonna put both when I order the numbers or just put one because it's just the same?
put both
@@betul-ev2fu thanks
I understand your formula for q1 and q3 works when for example n=12. Then the q1 is the 13/4 = 3.25 =3.5th value. But when n=10 then, according to your forumla q1 should be 11/4 = 2.75 = 2.5th value. But when I input data with n=10 in my TI84 calculator, the q1 is calculated to be 3rd value. I do not understand this. Can you explain?
Thanks very much!
I never divide by 4 in my examples. When n=10 the median would be the (10+1)/2 th value inotherwords the 5.5th value which is the mean of the 5th and 6th values. Now that the position of the median is found to be the 5.5th value you have 5 numbers below this. So to get the middle of this list of 5 values (The lower quartile) add 1 and divide by 2 so (5+1)/2 = 3rd value. I always use a system where the middle of any list of numbers is to add 1 and then divide by 2.
Hi, you said that the position of the median is to be 5.5th value and then you have "5 numbers below this", what about the 0.5 of a number you get rid of when you consider the median of those 5 numbers?
what if the median was 6.75 th value?
If you're using the (n+1)/2 formula, I don't think it's possible to get a 6.75th value. This is for discrete data, so the value of n is always an integer (There is no decimal point).
You see in many text books different ways of putting this across. I disagree with your method. An alternative method is to do 3/4(12+1)/4 which gives 9.75. Any decimal is rounded up or down to .5 so this is rounded down to 9.5, so inbetween the 9th and 10th values. For the lower quartile (12+1)/4 gives 3.25 so round up to 3.5 so in between 3rd and 4th values. I always teach my method though.
12+1 divided by 4 for example gives 3.25, what do you do then?
By this method you will not get that situation.
Hello can i use this even if i only have three set of data ex: 3, 5, 6. Thanks
Yes, you can, as long as you have more than one data point.
@@ExamSolutions_Maths Thank you sir, you have save my day.
@@johnlloydcruz2075 no problem.
why did you simplify the lower quartiles?
Not sure what you mean
In my S1 textbook, it says find n/4 or 3n/4 then if the result is a whole number, find the midpoint of the corresponding term and the term above and select that value; if not, always round UP then select the corresponding value. Would your method give the same result as this for all values of n? would it be accepted by edexcel as an answer? as I find your method simpler
Thanks
Anoop Rao There are a number of methods out there some I think are over complicated but will achieve the same answer. I prefer the method i use and it will get you the correct answer and be allowed.
Thank you very much :)
It wouldn't though. If you had 13 terms, the median using your method would be the 7th term, using the method on the book it would also be the 7th term, however it is the quartiles that give different answers. Using your method, Q1 would be the 3.5th term (6+1/2=3.5), however using the book method, it would be the 4th (13/4=3.25) due to rounding up when having a fraction.
If I'm mistaken, please let me know
Which book, which page?
😊
How can you have 10.5 if it is discrete data? If this was something to do with the amount of people, how can you have 10.5 people? I am so confused.
Wouldn't the Q2 for a) be 16.5?
12÷2=6
Applying the general formula for the lower quartile in your second example (denoted by n+1/4) results in the answer (3.25 not 3.5). Considering this formula is in the OCR textbook, I find it difficult to believe your final answers regarding the upper and lower quartiles in the second example are correct. Your error will have caused countless students confusion and stress. If you are going to make revision resources, please avoid discrepancies.
Sorry the video is good but there is a mistake on it!!!
to find UQ and LQ you do 3n/4 and n/4 respectively why do I get a different answer to you for Q3 on 2nd example
+Ishaq Miah Because your method is incorrect for discrete data.
+Ishaq Miah Do 3(n+1)/4 for UQ and (n+1)/4 for LQ you'll get correct answer