Average of unweighted data

rwf

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Jul 26, 2014
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I have some data from gas emission samples, part of the data was sampled in a region with a characteristic A and elsewhere with characteristic B. However, each region corresponds to a different percentage of total area.


I want to calculate the central value (average or median) of unbalanced with different weights data with the following characteristics:
- I have 35 observations in total, with 15 observations in group A and 20 in group B.
- The 20 observations of group B show average much higher (aprox. 40x higher) than group A.
- Group A corresponds to 58% and group B to 42% of my study area.


I used ponderate average to calculate overall average data:
((Average Group A * 0.58) + (0.42 * Average Group B)) / 2.
Am i right doing this?
And how can i calculate those overall median?

Thanks for your attention. :D
 
That will give "an" average but with only 35 observations, why not just average directly- the sum of all the values divided by 35?

The "median" is the middle number. Put the 35 observations in increasing order and pick out the 18th one. I don't see any accurate way of doing that with "averages" from the two groups separately.
 
That will give "an" average but with only 35 observations, why not just average directly- the sum of all the values divided by 35?

The "median" is the middle number. Put the 35 observations in increasing order and pick out the 18th one. I don't see any accurate way of doing that with "averages" from the two groups separately.

I can not do that because then I would overestimate the average since most of my observations correspond to higher values ​​(Group B), however, this group occupies only 42% of the study area. I am very uncertainly on how to apply this weight to each group and take the average of that.
 
I can not do that because then I would overestimate the average since most of my observations correspond to higher values ​​(Group B), however, this group occupies only 42% of the study area. I am very uncertainly on how to apply this weight to each group and take the average of that.
Since you said you wanted to find the average, how do you know what the average is to say that would "overestimate it"?
 
Since you said you wanted to find the average, how do you know what the average is to say that would "overestimate it"?

I think its overestimation because I am dealing with unbalanced data, moreover the weights do not represent the same proportion of the balance of the number of samplings. Therefore, I believe I would increase an average for the part of my system that already checked in another test that has higher and significant values ​​over the second. Dont you think?
 
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