In social science it is comon to use sample weight to post adjust the sample so that it fits to a given basci population. There are algorithms to calculate how many cases you need to have a representive sample of the population. But often we would like to analyse a bit deeper than just the sample as a whole e.g. male vs. female or age groups. Theoretically - if I'm not wrong - we need for each field a representive number of cases. So if I need 360 cases in the whole sample, I need for the analysis of male vs. female 360 * 2 (one for each field)
If we use weights, the question is on who many cases we the extrapolation is based. But how many cases I need at least to extrapolate my sample? I have the following table with observed cases per field:
Male || Female
Education || Education
age | low | middle| high | sum || low | middle| high | sum | SUM
---------+-------+-------+-------+----------++-------+-------+-------+-------+------
18 - 24 | 26 | 60 | 23 | 109 || 33 | 45 | 20 | 98 | 207
25 - 39 | 6 | 78 | 94 | 178 || 8 | 114 | 147 | 269 | 447
40 - 49 | 1 | 105 | 134 | 240 || 6 | 124 | 172 | 302 | 542
50 - 59 | 6 | 63 | 117 | 186 || 8 | 117 | 146 | 271 | 457
60 - 69 | 3 | 48 | 110 | 161 || 17 | 99 | 122 | 238 | 399
70+ | 7 | 30 | 75 | 112 || 41 | 89 | 58 | 188 | 300
---------+-------+-------+-------+----------++-------+-------+-------+-------+-------
SUM | 49 | 384 | 553 | 986 || 113 | 588 | 665 | 1366 | 2352
If we take a look at the males with a low education in the different agegroups, I have doubt, that we can extrapolate them. But I can't argue that right now. Even if we take just the low educated males at all, I don't think that the amount of cases are enough to extrapolate them.
What I have to do is to analyse injuries in sex, education leavel and age groups. But because of this distribution table I don't know, if the reslaults are representive for the basic population wich is over all about 2 million people.
So here my questions:
- How I can figure out if a number of cases is big enough to get extrapolated
- Do I really need, as I mentioned above, the amount of samples per field e.g. 360 males in the age of 18-24 with a low education level to analyse this group?
- On which categories (e.g. age groups, sex or combined) I can run representive calculations?
Maybe there is also something with which I can do the extrapolation with R and something like a test how good my extrapolation is...
Thanks for y'all help. Dominik