# Firefeather

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bio website location Columbus, OH age 30 member for 3 years, 1 month seen Dec 2 at 19:41 profile views 51

Statistical Packages I Use:

Other Related Software I Use:

College and Professional:

Statistical Topics I Know (Frequentist approach where applicable):

• Study design
• Experimental designs
• Factorial
• Fractional factorial
• Randomized block designs (RCBD, GRBD)
• Observational study designs
• Cross-sectional studies
• Longitudinal studies, specifically Cohort / Panel studies
• Retrospective studies
• Prospective studies
• Case-control studies
• Nested case-control studies
• Linear regression
• ANOVA
• Logistic and probit regression
• Tobit regression (self-taught)
• Truncated regression (self-taught)
• Nonparametric methods (and confidence intervals, where applicable)
• Scoring systems
• Permutation tests and confidence intervals
• Nonparametric tests and confidence intervals
• Nonparametric bootstrap testing, confidence intervals, and regression
• Smoothing techniques
 Sep10 awarded Notable Question Apr26 comment What happens to the covariance matrix when the errors are independent? Note the requirement of the assumption that the error terms all have the same variance; that is, $E(u_i) = 0 \forall i$ and $E(u_i^2) = \sigma^2 \forall i$. This is necessary for saying the covariance matrix has the same $\sigma^2$ value on all the diagonals. Mar20 awarded Self-Learner Mar5 awarded Notable Question Feb5 awarded Popular Question Oct11 comment Can we see shape of normal curve somewhere in nature? I'd argue that the Galton box is not an example of the Normal distribution, but instead, an example of a binomial distribution (with $p \approx 0.5$). After all, "discrete" is a closer description of the distribution than "continuous", and the distribution is bounded. Instead, the Galton box demonstrates the appropriateness of Normal approximation to a binomial distribution (or, equivalently, the Central Limit Theorem applied to the total of a sample from a Bernoulli distribution). Jul16 awarded Popular Question Jun4 comment How can I compute Pearson's $\chi^2$ test statistic for lack of fit on a logistic regression model in R? @Macro, you're very welcome! I wish I could ask more questions where I don't provide the answer, and answer more questions that I didn't ask. But jbowman's right about a pattern: my contributions to the community are tending toward talking to myself. :) (At least I'm contributing somehow to the community, right?) Jun4 comment How can I compute Pearson's $\chi^2$ test statistic for lack of fit on a logistic regression model in R? @Macro, please see this official link: blog.stackoverflow.com/2011/07/… (it's linked on the Ask a Question page in the checkbox label at the bottom: "Answer your own question – share your knowledge, Q&A-style"). I had this question while I was doing homework (having chosen to use R instead of Minitab, though Minitab was demonstrated in class), but I didn't have enough time to type up the question and wait for a response. I figured out this workaround, and decided to share it with the community. Jun1 answered How can I compute Pearson's $\chi^2$ test statistic for lack of fit on a logistic regression model in R? Jun1 asked How can I compute Pearson's $\chi^2$ test statistic for lack of fit on a logistic regression model in R? Apr2 comment What method is suitable for short-term forecast for a trendless, oscillatory, bounded time series? @Shelagh, perhaps, and nothing keeping people from answering you. However, the process will remain a "black box" to you, difficult to troubleshoot or explain to others who rely on your work. Best wishes! Mar22 awarded Organizer Mar22 revised What method is suitable for short-term forecast for a trendless, oscillatory, bounded time series? Removed irrelevant tags, made the title more specific Mar22 comment What method is suitable for short-term forecast for a trendless, oscillatory, bounded time series? @Shelagh, it seems to me that the root of your problem is that you lack a firm understanding of the basic concepts of time series analysis. Answering this question may help you temporarily, but you'll be better off in the long run if you study an introduction to time series. Mar22 suggested suggested edit on What method is suitable for short-term forecast for a trendless, oscillatory, bounded time series? Feb24 awarded Citizen Patrol Feb23 revised Poor predictions from lm.ridge? Added ridge-regression tag, a little formatting cleanup, and narrowing the question a little, introduction of the code block Feb23 suggested suggested edit on Poor predictions from lm.ridge? Dec16 awarded Popular Question