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# Interpolation watch

1. If I am given a data table like this:
(with a frequency column, not show)

Length of stay:
0 -
30 -
60 -
90 -
120 -
....

Do I assume the first group range is 0-30 or 0-29

why

(AS Edexcel examination, S1)
2. Question paper:http://www.thomas-reddington.com/upl..._solomon_l.pdf
Mark scheme: http://www.thomas-reddington.com/upl..._solomon_l.pdf

Look at question 7a to see what I mean.
I am fairly sure they got ALL the quartiles wrongly

Do you agree or not

----
e.g:
Q2 = 120/2 = 60
(14/32)*30 + 59.5

(59.5 = extended group boundary if we assume 0-29, ...)
I am fairly sure they got it wrong as it seems they have counted it as 0-30...
3. 0 - ....means 0<= t < 30 i.e. up to the lower class boundary of the next group.
30 - ....means 30<= t < 60
60 - ....means 60<= t < 90
etc..
So Q2 = 60 + (14/32)*30 where 60 is the lower class boundary of the group containing the median.
4. ok then

thanks

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