stats - SIR, min and max values??

lou_needs_maths_help · 2010-01-20 20:35:06

Hi does anyone know how i can find the minimum and maximum values and the semi interquartile range for this data?

mean - 550
median - 470
lower quartile - 300
upper quartile - 670
standard deviation - 115
number of employees - 248

Thankyou

bobbym · 2010-01-20 21:08:15

Hi;

The semi interquartile range is computed as one half the difference between the 75th percentile [often called (Q3)] and the 25th percentile (Q1). The formula for semi-interquartile range is therefore: (Q3-Q1)/2

lou_needs_maths_help · 2010-01-20 21:12:31

Hi thank you, that's what Ive done so now I know it is right however in the notes given in class it says
Q1 = Median - SIR
Q3 = Median + SIR

Using the formula the SIR would be 185 but this doesn't fit with the above formula for both Q1 and Q3?

bobbym · 2010-01-20 21:17:13

What have you computed Q3 and Q1 to be?

lou_needs_maths_help · 2010-01-20 21:21:31

for this question I am given Q1(lower quartile) and Q3(upper quartile) - 300 and 670

so the formulas I have in my notes contradict
(Q3-Q1)/2
and
Q1 = Median - SIR
Q3 = Median + SIR

do not both work! Sorry I should have been clearer - not sure which one to use!

lou_needs_maths_help · 2010-01-20 21:23:40

O another thing is the median is 470, Q1 is 300 and Q3 is 670 so what i have in my notes:

Q1 and Q3 can be found using the approximate rules
Q1 = Median - SIR
Q3 = Median + SIR

doesn't make sense with the numbers I have!?!

bobbym · 2010-01-20 21:24:24

Are you sure that your median is correct?

lou_needs_maths_help · 2010-01-20 21:30:39

yes because it is given to me in the question the data I have been given is:

mean - 550
median - 470
lower quartile - 300
upper quartile - 670
standard deviation - 115
number of employees - 248

So it really doesn't make sense unless I am completely missing something?!

lou_needs_maths_help · 2010-01-20 21:33:08

and I have to find out:
range (I have no idea how to find the minimum and maximum with the data I have been given?)
semi interquartile range (not sure because of the above)
weekly total salaries - 248x550
shape of distribution - positively skewed as mean > median

bobbym · 2010-01-20 21:33:53

Hi;

According to your formulas the median should be smack in the middle of Q1 and Q3, the fact that it isn't is the surest evidence that whomever computed the median didn't do it right. The median depends on the data, without the data how can I fix it?

lou_needs_maths_help · 2010-01-20 21:41:03

Hi I haven't been given the data all I have is what is above and I have to work out range and SIR based on the information given. The median is 50% of the values though so surely it should be right in the middle of Q1 and Q3. It is my university assignment so I doubt that the figures they have given are wrong because the whole class would fail

I think im gonna stick with (Q3-Q1)/2 and ignore the other formula I have been given as they cannot both be right.

Do you know how I can find the minimum and maximum values so I can find the range?

bobbym · 2010-01-20 21:50:03

The range as I understand it is the difference between the highest and lowest values of the data. Do you see how to get that from what you have provided?

bobbym · 2010-01-20 21:56:49

Here is some useful pages for you to review:

http://www.mathsteacher.com.au/year9/ch … rtiles.htm

http://www.mathsteacher.com.au/year9/ch … .htm#range

This last link is of great importance because it will tell you how to compute the SIR

http://www.shodor.org/interactivate/dis … s/BoxPlot/

lou_needs_maths_help · 2010-01-20 21:57:08

um no I dont know how to get it, yes range is difference between max and min values

is it median - Q1 for the minimum and median + Q3 for the maximum? that is only a guess Im really not sure, we do not have a formula for it in our notes!

lou_needs_maths_help · 2010-01-20 22:01:43

ohh no that definitely isn't right umm i have no idea then

bobbym · 2010-01-20 22:04:42

Are you trying to find the range or the SIR, they are not the same.

lou_needs_maths_help · 2010-01-20 22:07:30

Hi thanks for the links but I do not have a list of data to see what the min and max values are, if I had them I know how to work out the range, I just dont know the formula to work out out min and max without the data, do you know how to do it?
sorry I know you dont have to help me but I need to leave to hand it in in 50 mins and really need to pass or I will have to resit the entire module next year

lou_needs_maths_help · 2010-01-20 22:08:54

Hi

I am gonna leave the SIR as 185 because atleast one formula we were given supports it

I just need to find the minimum and maximum numbers so I can work out the range

bobbym · 2010-01-20 22:13:03

I am trying everything I know, the last link describes getting the Interquartile range, it is done by subtracting Q3 - Q1 that seems to be the only range you can get. Maybe that is what they require.

lou_needs_maths_help · 2010-01-20 22:17:37

It cant be because I have to find the range and the interquartile range, I am 99% sure the interquartile range is 185 but really dont know how to find minimum and maximum values with no data

bobbym · 2010-01-20 22:23:24

Q3 - Q1 = 370 this is the interquartile range. The 185 is the Semi interquartile range. which is 1/2 of the interquartile range. See what I am getting at?

lou_needs_maths_help · 2010-01-20 22:27:15

ohh yes ok I have got it but i need just the range not the interquartile range.
could this work to find out range:
mean+ (standard deviation x 3) - mean - (standard deviation x 3)

???

bobbym · 2010-01-20 22:36:22

Thats an idea, and a good one but I don't know if there is any justification for it. Why use 3 sd's why not 4 or 5 see what I am saying.

lou_needs_maths_help · 2010-01-20 22:39:47

well i found it in my notes, it does say it works best for symmetrical skew, and this is positive but considering the time i guess im gonna have to go with it and hope it is right!

Better go and print it all off

Thank you so much for all your help

bobbym · 2010-01-20 22:41:55

Hi Louise;

I think that is your name, you have a fairly good grasp of these principles so don't paint yourself into a corner ever again. Cramming is awful, don't do it anymore. Hope you do well.

Math Is Fun Forum

#1 2010-01-20 20:35:06

stats - SIR, min and max values??

#2 2010-01-20 21:08:15

Re: stats - SIR, min and max values??

#3 2010-01-20 21:12:31

Re: stats - SIR, min and max values??

#4 2010-01-20 21:17:13

Re: stats - SIR, min and max values??

#5 2010-01-20 21:21:31

Re: stats - SIR, min and max values??

#6 2010-01-20 21:23:40

Re: stats - SIR, min and max values??

#7 2010-01-20 21:24:24

Re: stats - SIR, min and max values??

#8 2010-01-20 21:30:39

Re: stats - SIR, min and max values??

#9 2010-01-20 21:33:08

Re: stats - SIR, min and max values??

#10 2010-01-20 21:33:53

Re: stats - SIR, min and max values??

#11 2010-01-20 21:41:03

Re: stats - SIR, min and max values??

#12 2010-01-20 21:50:03

Re: stats - SIR, min and max values??

#13 2010-01-20 21:56:49

Re: stats - SIR, min and max values??

#14 2010-01-20 21:57:08

Re: stats - SIR, min and max values??

#15 2010-01-20 22:01:43

Re: stats - SIR, min and max values??

#16 2010-01-20 22:04:42

Re: stats - SIR, min and max values??

#17 2010-01-20 22:07:30

Re: stats - SIR, min and max values??

#18 2010-01-20 22:08:54

Re: stats - SIR, min and max values??

#19 2010-01-20 22:13:03

Re: stats - SIR, min and max values??

#20 2010-01-20 22:17:37

Re: stats - SIR, min and max values??

#21 2010-01-20 22:23:24

Re: stats - SIR, min and max values??

#22 2010-01-20 22:27:15

Re: stats - SIR, min and max values??

#23 2010-01-20 22:36:22

Re: stats - SIR, min and max values??

#24 2010-01-20 22:39:47

Re: stats - SIR, min and max values??

#25 2010-01-20 22:41:55

Re: stats - SIR, min and max values??

Board footer