Top new questions this week:
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I am trying to run a nls() to interpolate height growth of a tree given a series of samples, where each sample has a value of age, and height. I am using the Richards (1959) method: $$ \textrm{Height}=…
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It is a well-known fact that the minimizer of the mean-squared loss (MSE) $$\min\limits_\mu \mathbb{E}_{X} \left(X – \mu \right)^2$$ equals the expectation of $X$. Are there any alternative non-…
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I am struggling to derive the following identities: $$ \mathbb{E}[\log Z]=2\log(\mathbb{E}[Z])-\frac12\log(\mathbb{E}[Z^2]) $$ $$ \mathrm{Var}[\log Z]=\log(\mathbb{E}[Z^2])-2\log(\mathbb{E}[Z]) $$ …
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I have been trying to reconcile R coefficients with actual coefficients for simulated data which follows the equation: $$ y = \alpha + \beta \cdot f(x) + \epsilon $$ where $\alpha$ is intercept and $\…
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I have a small data set which (a) is always positive and (b) is showing a right tail on the histogram. I wondered if it could be log-normal and tested for this, but to no avail. I am now wondering …
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I wish to test whether a large number of observations $X_i$ follows an exponential distribution with parameter $\lambda=1$. I also wish to test this hypothesis exactly, and intend that if the …
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Suppose $p(x) = \lambda e^{-\lambda x}$. However, our probability of observing a given sample of $x$ (denoted $z$) is further proportional to $x$ itself, i.e., $p(z\mid x) = \lambda e^{-\lambda x}$. …
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Greatest hits from previous weeks:
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My understanding was that descriptive statistics quantitatively described features of a data sample, while inferential statistics made inferences about the populations from which samples were drawn. …
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I am wondering how to choose a predictive model after doing K-fold cross-validation. This may be awkwardly phrased, so let me explain in more detail: whenever I run K-fold cross-validation, I use K …
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…assuming that I’m able to augment their knowledge about variance in an intuitive fashion ( Understanding “variance” intuitively ) or by saying: It’s the average distance of the data …
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The waiting times for poisson distribution is an exponential distribution with parameter lambda. But I don’t understand it. Poisson models the number of arrivals per unit of time for example. How is …
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Data analysis cartoons can be useful for many reasons: they help communicate; they show that quantitative people have a sense of humor too; they can instigate good teaching moments; and they can help …
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I am working with a small dataset (21 observations) and have the following normal QQ plot in R: Seeing that the plot does not support normality, what could I infer about the underlying distribution? …
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What is your favorite statistical quote? This is community wiki, so please one quote per answer.
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Can you answer these questions?
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I am working on a meta-analysis of travel impact measures where I have the total measurements and the specific amount of increase or decrease. In each study, I have multiple scenarios for the …
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I am working on a paper on smoking and depression in a sample of approximately n=2.000 subjects, and for that, I use longitudinal data (5 waves, 2 years between each wave). For a part of the paper, I …
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Suppose I have $q$ censored covariates, say $X_1, \ldots, X_q$ which are all left-censored with censoring values $\mathbf{d} = d_1, \ldots, d_q$. If I assume that the $X_i$ are from some multivariate …
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