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170
votes
What intuitive explanation is there for the central limit theorem?
The mathematical description of this is that for each $n$ we can choose some central value $m_n$ (not necessarily unique!) … Why don't we have central limit theorems for other mathematical combinations of numbers such as their product or their maximum? …
126
votes
Accepted
T-test for non normal when N>50?
By the central limit theorem, means of samples from a population with finite variance approach a normal distribution regardless of the distribution of the population. …
116
votes
Accepted
Pearson's or Spearman's correlation with non-normal data
The distribution of either correlation coefficient will depend on the underlying distribution, although both are asymptotically normal because of the central limit theorem. …
115
votes
Why does a time series have to be stationary?
It turns out that a lot of nice results which holds for independent random variables (law of large numbers, central limit theorem to name a few) hold for stationary random variables (we should strictly … It turns out that any stationary data can be approximated with
stationary ARMA model, thanks to Wold decomposition theorem. …
113
votes
Accepted
Consider the sum of $n$ uniform distributions on $[0,1]$, or $Z_n$. Why does the cusp in the...
Dividing both sides by $dt$ and taking the limit as $dt\to 0$ gives
$$f_{X+Y}(t) = F_Y(t) - F_Y(t-1).$$
In other words, adding a Uniform $[0,1]$ variable $X$ to any variable $Y$ changes the pdf $f_Y$ … The Central Limit Theorem has little to say here. After all, a sum of iid Binomial variables converges to a Normal distribution, but that sum is always discrete: it never even has a PDF at all! …
97
votes
What is a complete list of the usual assumptions for linear regression?
If $y_i$ are not normal, but independent, we can get approximate distribution of $\hat\bet$ thanks to the central limit theorem. … The central limit theorem then gives us the following result:
$$\sqrt{n}(\hat\bet - \bet) \to \mathcal{N}\left(0, A^{-1} B A^{-1} \right).$$
So from this we see that independence and constant variance …
92
votes
Accepted
How to choose between t-test or non-parametric test e.g. Wilcoxon in small samples
To make matters worse, it is unsafe to use the Central Limit Theorem as a safety net: for small n we can't rely on the convenient asymptotic normality of the test statistic and t distribution. … CLT for the numerator, and Slutsky’s theorem suggest that eventually the t-statistic should begin to look normal, if the conditions for both hold.) …
91
votes
Accepted
How does saddlepoint approximation work?
limit theorem. … So, it will only work in settings where there is a central limit theorem, but it needs stronger assumptions. …
89
votes
Central limit theorem for sample medians
are histograms of the median positions:
Clearly, for a sufficiently large number of atoms, the distribution of their median position begins to look bell-shaped and grows narrower: that looks like a Central … Limit Theorem result, doesn't it? …
77
votes
What is the trade-off between batch size and number of iterations to train a neural network?
And if your data truly is IID, then the central limit theorem on variation of random processes would also suggest that those ranges are a reasonable approximation of the full gradient. …
73
votes
Accepted
40,000 neuroscience papers might be wrong
The smoothing also
affects the assumption that the residuals are normally distributed, as
smoothing, by the central limit theorem, will make the data more
Gaussian. …
71
votes
Accepted
Regression when the OLS residuals are not normally distributed
Edit: I often hear it said that you can rely on the Central Limit Theorem to take care of non-normal errors - this is not always true (I'm not just talking about counterexamples where the theorem fails … Limit Theorem to give you approximately unbiased inference for realistic finite sample sizes. …
68
votes
T-test for non normal when N>50?
The central limit theorem is less useful than one might think in this context. First, as someone pointed out already, one does not know if the current sample size is "large enough". …
65
votes
Accepted
Assumptions regarding bootstrap estimates of uncertainty
To construct a confidence interval (which is, essentially, what the bootstrap is all about), we can use the central limit theorem, the consistency of empirical quantiles and the delta method as tools to …
60
votes
Accepted
Central limit theorem for sample medians
$Z_i = 1$ if $X_i \leq x$ and $0$ otherwise), you can directly apply the Central limit theorem to a mean of $Z$'s, and by using the Delta method, turn that into an asymptotic normal distribution for $F_X …