Dear members,
Thank you for your replies.
I have been advised to group my data in intervals around the weights of my interest. Then I could assume these data to be representative of the distribution for the exact value (65kg, 70kg,...) from where calculating the percentiles.
This would be the classical approach but I have found very few values around some of the points of interest. I wonder if I could use probability with these data, may be conditional or joint distributions to answer questions such as:
Having a 80kg man, what would need to be his blood pressure for this man to be in the lowest 25% blood pressure group among the 80kg men?
P((BP<=X inters W=80)/W=80)=0.25 ???
I would greatly appreciate any more suggestions.
Thank you all for your replies.
Best regards,
Oscar.
--- El sáb, 22/1/11, Óscar Martín Camacho <[log in to unmask]> escribió:
De: Óscar Martín Camacho <[log in to unmask]>
Asunto: Rv: Percentiles
Para: [log in to unmask]
Fecha: sábado, 22 de enero, 2011 13:51
Dear list members,
It seems I was not clear. Thank you for letting me know.
Simplifying, I have 2 continuous variables Weight and Blood Pressure taken to 1100 men. They are presented in 1 decimal place units: one observation was 1 man with 79.7 kg and 115 mmHg.
With these data. How could I calcilate the percentiles 25, 50 and 75 with respect to blood pressure of a 80 kg man. My table would looks like:
Weight percentile 25 (blood pressure)
80 kg
--- El sáb, 22/1/11, Óscar Martín Camacho <[log in to unmask]> escribió:
De: Óscar Martín Camacho <[log in to unmask]>
Asunto: Percentiles
Para: [log in to unmask]
Fecha: sábado, 22 de enero, 2011 12:34
Hello,
I am trying to characterise descriptively the weight of a group of men with respect to their systolic blood pressure. An extract of the two variables can be seen below:
Weight (kg) Blood P(mm)Hg
81.4 123
64.7 119
72.1 115
There are 1100 in total.
I would like to make a table with percentiles for these groups of men from 65kg to 80kg by intervals of 5kg with respect to blood pressure. Example:
Weight Percentile25 percentile50 percentile75
65kg 109mmHg 114mmHg 118mmHg
70kg 108mmHg 116mmHg 120mmHg
75kg 109mmHg 117mmHg 120mmHg
80kg 112mmHg 119mmHg 122mmHg
My problem is that the weights are not in these same measures so I am not sure how this interpolation could be made.
I would appreciate any suggestions about how to proceed.
Best regards,
Oscar
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