j.persephone

Very cool. I have been curious about this and how it's taught at other programs for a while. Thank you so much for your detailed replies!

Hello again, Thank you for your replies. To give the most basic example of what I am talking about, let's say you have data on all countries from 1945-1995 and you want to run some regression where you could calculate/Stata will tell you p-values. Some articles will do this and then talk about their coefficients being statistically significant and imply that this matters for all the reasons statistical significance would matter (all I meant by "interpreting"). The problem here is that some people think p-values in this scenario would be either irrelevant or dubiously applied. If this data is best thought of as population data, p-values would be irrelevant. When people decide to interpret it anyways, they will often make the appeal to the theoretically larger superpopulation argument which I mentioned in my original post. This goes basically as reasonablepie described it, that there are always future/past or even hypothetical cases that make it reasonable to talk about the statistical significance of what you have found. The problem with this is that our "sample" of this population, all countries from 1945-1995, is in no way a random or even a probability sample of this theoretical superpopulation and measures like p-values are to my knowledge based on the properties of random sampling. For this reason, some would say interpreting p-values in this case would be dubious at best. I have read in other forums that people use p-values in things like our example because the result is mathematically a reasonably good approximation of tests that we "should" be using because they are less problematic in their theoretical grounding. However, I have been unable to find a citation for this. I was hoping someone might have an answer and I was also legitimately curious what people were learning in other programs. If I am still not communicating this in a way that makes any sense, here is a link to the debate I am talking about: Critique: http://www.jstor.org/stable/30011818 Author's Reply: http://www.jstor.org/stable/30011819 And here is another helpful post: http://stats.stackexchange.com/questions/2628/statistical-inference-when-the-sample-is-the-population Thank you all so much!

Hi everyone, Let me start by saying, if this part of the forum is only supposed to be for admissions questions, I apologize. I was hoping to get some insight into a question about statistics in political science. As an undergrad, I was taught that if you are using population data, even if it is a limited temporal scope (e.g. all countries between 1945-1995), there is no reason to interpret statistical significance. Even though the units are part of a theoretically larger population and it would be useful to know the thing statistical significance is trying to get at, using methods that are actually based around the properties of random sampling does not really tell you anything particularly meaningful. I'm now in an MA program where I have some professors who subscribe to this and others who adamantly do not. I have noticed plenty of articles do interpret statistical significance while using what is arguably population data or at least in no way a random sample. I would love it if anyone would be willing to share any insight on: 1) The status of this debate in the field more recently. Most of the articles on this that I have found are 10+ years old and I'm wondering whether a sort of unspoken consensus has been formed, or whether I have just been looking for discussions of this in the wrong places. 2) What are you teaching/being taught about the appropriateness of interpreting statistical significance with population data in your program? Sorry if I am using some terms imprecisely or not explaining this well. The language of instruction for my undergraduate courses was not English so I may not have translated my thoughts well. Thanks everyone and have a great weekend! B.

That makes sense. Thank you so much!

Hi there! Thank you all so much for your advice. If a program says a writing sample is optional, under what conditions would you recommend sending one? I had 98-99th percentile scores on the Verbal and AWA section of the GRE, so the admissions committee should not have strong reasons to doubt my writing ability. I discuss research ideas in the SOP that I hope are a compelling demonstration of my ability to think about new directions political science research. The main disadvantage to sending one would be that my best writing samples are somewhat outside of the research I want to do in the future (same subfield, totally different topics). The advice I have gotten has been mixed. I would really appreciate any insight you have.