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Full Version: Help with a Sample Statistical Calculation in an Online Tutorial
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I'm working on a doctoral dissertation in linguistics, and while I wait for enough people to sign up and participate in my experiment, I've decided to take a course or two on random variable distributions and statistical analysis on Brilliant.Org, so that when the time comes to analyze the data, I'll at least have a better clue as to what I'm doing.  One thing I've always hated about reading academic papers is that virtually every single one of them eventually reaches a point where they just start spewing statistical jargon at me (two-tailed t-tests and other such gobbledygook).  I know what a p-value is, I know roughly how linear regression works and what an R-squared or chi-squared value is, but beyond that, most of it's still Greek to me.

Personally, I don't get why they can't segregate the statistical nitty-gritty in an appendix.  That way, it would be there for the peer reviewers but wouldn't bog down those who are only interested in the broad trends and conclusions provided by the body of the paper.  I'm a linguist, not a f**kin' statistician.  Thanks to a book loaned to me by a professor, I finally have some idea about what the hell a t-test is, but I'd still feel better if I had a firmer grasp on this stuff, which is why I'm hacking my way through the online course.  There are courses at my university like "Statistics for Social Science," but the timing just never seems to have worked out for me to take one.  And yes, maybe I don't need to know the actual math behind the various analytical methods as long as I know which one to use, but I feel like having at least some foundation in the former would help in developing a sense for the latter.

Anyway, with that mini-rant off my chest, I have a question for any math/statistics nerds on here.  This has been driving me crazy.  It's a section on Poisson variables in the Brilliant tutorial.

[Image: Lambda.jpg]

What has me stumped is the third-to-last line.  I cannot for the life of me figure out where the λ^2 is coming from.  If it were λn in its place, that would make sense, but λ^2?  Is there an identity with sums that I'm missing or something?  Any help will be much appreciated!
Είναι ελληνικό για μένα.   hobo