Monica, There are three issues here: 1. the representativeness of your sample with respect to your target population (illicit drug users who used internet message boards) 2. the analysis that you can do with your sample and 3. What, given 1, you can say from the results of 2 about the target population 1. is tricky - you don't have any data (or do you? Does anyone else?) on the constitution of the target population. So you can't say how biased your sample is. It may not be biased - you may have a representative sample along key dimensions for your analysis. But how do you tell? This is a problem for all surveys of 'sensitive' issues. The usual resolution is to weight your sample so that on key dimensions it is representative of the target population. But this can only be done if you know the constitution of the target population with respect to these dimensions.... 2. the analysis. You can certainly do things like regression analysis with your sample. The 'statistical significance' simply tells you how confident you can be that any statistical effect is real (i.e. non random) for the sample. 3. Your problem is that, given 1 you may not be able to make claims from the results of 2 about the population - merely what you found in your sample. If the sample is biased but you can weight it to account for this bias (see 1) then your analysis results for the sample can be claimed to be true of the target population. Others may have different views :-) Ben On 3 Sep 2009, at 03:12, Monica Barratt wrote:
Hi everyone
I'm currently writing up my thesis which has the working title 'Researching the forums: Illicit drug use in a networked world'. I conducted an online survey using a purposive (nonprobability) sample of illicit drug users who used internet message boards (forums) to discuss or read about drugs. Originally I intended to conduct inferential statistics on this sample of 915, as this is the general practice in many other papers I had read. After some more thought though, I'm leaning away from that.
---- Dr Ben Anderson Sociology @ Essex http://www.essex.ac.uk/sociology/staff/profile.aspx?ID=118 Centre for Research on Economic Sociology and Innovation http://cresi.wordpress.com