question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>In a standard regression problem</p>
<p>\begin{equation}
\mathbf{y} = \mathbf{X} \beta + \mathbf{e} \ ,
\end{equation}</p>
<p>the solution to $\beta$ when the system is overdetermined is $\hat{\beta}= \left(\mathbf{X}\Sigma^{-1}\mathbf{X}\right)^{-1}\mathbf{X}^T\Sigma^{-1}\mathbf{y}$, where $\Sigma = \sigma^{-2} \... | 69,732 |
<p><strong>The Setup:</strong> Let $X_t$ denote an unobservable stochastic sequence where the first two <em>unconditional</em> moments are finite constants; ie $\mathbb{E} X_t = \mu < \infty$ and $\mathbb{E} X_t^2 = \gamma < \infty$. Assume that $X_t$ obeys some minimum set of regularity conditions such that a we... | 69,733 |
<p>I have an unbalanced data and I want to use LIBSVM from MATLAB. LIBSVM has two different parameters for cost: -c and -wi. What is the difference between them?</p> | 41,770 |
<p>I have 1 variable measured for 8 samples. so, for e.g. height of 8 men. I want to say something about: if height of men is significantly different amongst them. How can I do this?</p>
<p>Without any reference theoretical mean, I can not do a simple t-test.</p> | 69,734 |
<p>I have been asked to comment on a statistical analysis proposal that suggests using simultaneous equation modelling as a method. I have a basic general knowledge of statistics (Masters level) but very little experience with econometrics-specific modelling.</p>
<p>Does this technique go by any other name?
If it is ... | 69,735 |
<p>I have a dataset where the number of negative labeled values is 163 times the number of positive labeled values. That is, I have an unbalanced data set. I tried:</p>
<pre><code>model = svmtrain(trainLabels, trainFeatures, '-h 0 -b 1 -s 0 -c 10 -w1 163 -w-1 1');
[predicted_label, accuracy, prob_estimates] = svmpredi... | 39,602 |
<p>I have a binary response variable (0,1) with 300 (approximately) normally distributed variables as predictors all on (0,1). The training set has only 250 observations and the test set has approx. 20k observations. The goal is to make a model to best classify the test set observations as either 0 or 1. (it's an ap... | 69,736 |
<p>I'm trying to understand a very basic concept of standard deviation.</p>
<p>From the formula $\sigma= \sqrt{ \dfrac{ \sum\limits_{i=1}^n (x_i-\mu)^2} N } $</p>
<p>I can't understand why should we halve the population "N" i.e why do we want to take $\sqrt{N}$ when we didnt do ${N^2}$? Doesn't that skew the populat... | 30,337 |
<p>I am working on a short panel of 3 periods with a few hundred subject, and as the question and as the question suggests, I have some blanks. I know that there are not due to attrition since it is rating data of microfinance institutions and ratings have always been issued (each rating takes 3 years of accounting inf... | 30,338 |
<p>Suppose that you have ten years of monthly sales data and are interested in forecasting future sales. Consider the simple model
$$\begin{equation*} y_t = \alpha_m + \beta a_t + y_{t-1} + \epsilon_t, \end{equation*}$$
where $y_t$ is log monthly sales, $\alpha_m$ is a monthly fixed effect and $a_t$ is the year at time... | 40,663 |
<p>I have defined an distance measure based on some properties of points. But I'm not even sure that it corresponds to a valid distance in some vector space. Is this a necessary condition for clustering ? If yes, how do I check that it's a valid distance in some vector space. Just like Mercer's theorem can verify that ... | 30,341 |
<p>Assume, the model we are trying to estimate is:</p>
<p>$Y=\beta_ß+\beta_1X+U$</p>
<p>where x and u are correlated: $Cov(X,U)\neq 0$</p>
<p>Then OLS is inconsistent:</p>
<p>$\beta_1^{OLS}=\frac{Cov(Y,X)}{Var(X)}=\frac{Cov(\beta_0+\beta_1X+U,X)}{Var(X)}=\beta_1\frac{Cov(X,X)}{Var(X)}+\frac{Cov(X,U)}{Var(X)}=\beta_... | 69,737 |
<p>I'm trying to figure out a way for calculating price optimization in a commerce environment. In other words, I'm trying to analyze how a company can increase revenue and profitability by analyzing costs, customer buying behaviors, competitive activity, demand signals and historic data. </p>
<p>How can I come up wit... | 69,738 |
<blockquote>
<p>If $X$ is symmetrically distributed about zero , then show that $U=|X|$ and
$$V = \left\{
\begin{array}{}
+1, & X \geq0 \\
-1, & X<0
\end{array}
\right .$$
are independently distributed and interpret the result.</p>
</blockquote>
<p>Here distr... | 31,296 |
<p><a href="http://www.springerimages.com/Images/Geosciences/1-10.1007_s10933-008-9218-2-3" rel="nofollow">This</a> is pretty close from what I would like to do.</p>
<p><img src="http://i.stack.imgur.com/vr9ET.jpg" alt="enter image description here"></p>
<p>More precisely, I would like to represent graphically a sequ... | 44,922 |
<p>I am estimating a multinomial logistic model with R (package "mlogit"). I use the estimated coefficients to get the estimated odds and then I apply the Delta Method (package "deltamethod") to get robust standard errors.
So far, I am following the instructions <a href="http://www.ats.ucla.edu/stat/r/faq/deltamethod.... | 69,739 |
<p>Is taking the average of different rmse valid? for example
average rmse = (rmse1+rmse2+rmse3)/3
Thank you for your help!</p> | 69,740 |
<p>What is the Kullback-Leibler divergence for a Pareto Distribution? </p>
<p>Given $p(x)$ = $ \alpha$ $\frac{x^{\alpha}_{min,1}}{x^{a+1}}$.</p> | 69,741 |
<p>How would you model risk aversion in an automated planner?</p>
<p><a href="http://planning.cs.uiuc.edu/node467.html" rel="nofollow">This section in Planning Algorithms</a>, briefly talks about this, but doesn't really describe a solution. However, example 4 is an interesting scenario:</p>
<pre><code>Suppose that y... | 30,348 |
<p><strong>Question:</strong></p>
<p>Having performanced a linear regression in R with the lm function, I'm not sure how to interpret the results for the <em>Intercept</em> (as shown below). </p>
<p>It seems the probability of the intercept's relevance is low (i.e. <em>Pr(>|t|)</em> is 0.845, and higher that 0.05). D... | 49,302 |
<p>It is well known that estimating large covariance matrices from small samples is problematic. For instance, the $p \times p$ sample covariance matrix $\Sigma_n$, estimated from $n$ samples, is not necessarily a consistent estimator of the true covariance matrix $\Sigma$ when $p > n$.</p>
<p>In contrast, I am int... | 30,349 |
<p>What is a good resource that explains Bayesian statistics for an experimental scientists who already use Frequentist statistics? What are the Bayesian analogues for all the tools working scientists use, like ANOVA and linear regression (and how do the Bayesian analogues compare), and what software can be used to per... | 69,742 |
<p>If $F_i = G(F_{i-1}), F_0 = x$ is a sequence of distributions that converges to a degenerate distribution as $i \to \infty$, does that imply that the variance of $F_i$ decreases with $i$? </p>
<p>Specifically, I am interested in the inverse Kumaraswamy distribution: $G(x) = (1-(1-x)^a)^b$ when $a=b$... Note that $... | 69,743 |
<p>I would like to estimate the measurement error when aggregating (via arithmetic mean) gridded spatial data. The goal is to come up with the mean elevation (or some other spatially continuous variable) +/- some measure of uncertainty for each aggregated region. However, spatial data is more often than not spatially ... | 69,744 |
<p>I have a treatment sample of 200 firms. I'm using propensity score matching to pair each treatment observation with one control (sampling with replacement, in order to minimize bias associated with poor matches). This results in a sample of only 102 unique control firms (many of them are matched to multiple treatm... | 30,351 |
<p>I am using the <code>ADinf</code> procedure of <a href="http://www.jstatsoft.org/v09/i02" rel="nofollow">Marsaglia & Marsaglia</a> to compute the CDF of the Anderson Darling statistic. I am interested in the survival function, 1 minus the CDF, for large values of the test statistic. The implementation given by M... | 30,352 |
<p>I have found no tool to estimate an "oprobit"-like ordinal model using the local regression (local likelihood) framework. It's not built into R's locfit. What is a good way to proceed?</p>
<p>Example:
I have a predictor $x\in [-1,1]$, and outcome $y\in\{1,2,3,4,5\}$. I would like to non parametrically predict (trac... | 69,745 |
<p>I have a database with 200+ variables and less then 50 cases. I need to choose an optimal model that predicts one dependent variable. </p>
<p>Are stepwise/lasso regressions still appropriate methods to build such model?</p> | 69,746 |
<p>Has two one-sided tests for equivalence (TOST) been framed for the Kolmogorov–Smirnov test to test the negativist null hypothesis that two distributions <em>differ</em> by at least some researcher-specified level?</p>
<p>If not TOST, then some other form of equivalence test?</p>
<p>Nick Stauner wisely points out t... | 69,747 |
<p>I am doing a review of statistical methodology used for microRNA data obtained from Affymetrix platform. I have data from 178 patients and their prognosis information as well
as recurrence of disease and survival outcome (dead,alive).</p>
<p>I learnt that I can treat recurrence rate to separate patients into two gr... | 69,748 |
<p>Can anyone explain the primary differences between conditional inference trees (<code>ctree</code> from <code>party</code> package in R) compared to the more traditional decision tree algorithms (such as <code>rpart</code> in R)?</p>
<ol>
<li>What makes CI trees different?</li>
<li>Strengths and weaknesses?</li>
</... | 231 |
<p>Homework problem asks to compute the principal components of a p-variate multinormal vector $X$ ~ $N(0,\Sigma)$ where $\Sigma$ = $\delta^{2}I_{p} + \sigma ^{2} I_{p}I_{p}^{T}$. I use the PC transformation from our multivariate text where the rows of Y are the PCs and $\Gamma ^{T}$ is matrix of eigenvectors for the d... | 69,749 |
<p>I have been using a statistic to measure "influence" or some analogous concept in the following way:</p>
<p>First calculate the mean for a given sample, then calculate the mean for the given sample <em>excluding</em> each observation in turn. Subtract the latter from the former. The result is a vector measuring the... | 69,750 |
<p>I have this problem: In betting situations one is often interested in odds, referring in the thumbtack tossing $\theta / (1 - \theta)$. Alternatively one may consider the log-odds:</p>
<p>$\lambda=log(\theta/(1-\theta))$</p>
<p>Show that a uniform distribution for $\lambda$ implies the following distribution for $... | 69,751 |
<p>I've conducted an ordinal regression with two categorical variable (attitude toward fraud or probability of being caught=punishment). attitude range is 1:no wrong to 4:very wrong. probability of being caught range is 1:unlikely to 4: very likely. the research question is whether attitude toward fraud or probability ... | 30,357 |
<p>I am looking for an estimator of the mean of normally distributed data (with known variance) in the regime where the sampling grid is much coarser than the variance. I.e. in the worst case consider count data where only two bins contain data points.</p>
<p>For example assume I sampled 40 data points from a normal d... | 49,770 |
<p>Does the computation of an N x N correlation matrix for N unrelated variables require multiple comparisons correction for all the computed pairwise correlations (assuming each computed correlation is a 'comparison' in the sense of being a 'statistical test')? If so, would FWER be a more appropriate measure than Bonf... | 30,358 |
<p>I want to fit a nonlinear mixed effects model for repeated measures data. The subjects on which the measures were repeated are spatially structured. Is there a package in R for this? I also have access to Stata, SAS, Mplus, and Mathematica.</p>
<p>Alternatively, is it acceptable to just include random effects for ... | 69,752 |
<p>I have a logistic model with 8 variables. I ran a chi square test in R (anova(glm.model,test='Chisq')) and 2 of the variables turn out to be predictive when ordered at the top of the test and not so much when ordered at the bottom. the summary(glm.model) suggests that their coefficients are insignificant (high p-val... | 69,753 |
<p>Can someone please explain Maximum Likelihood Estimation in very lay-man terms? I understand that the Likelihood function is obtained by multiplying all the probabilities in the distribution. Or if I am wrong, please correct.</p> | 40,689 |
<p>I have several data sets that gathered similar data on a similar population group in one setting. Can I simply combine the data on common variables or do I need to engage in some pooled analysis?</p> | 30,360 |
<p>I would like to model intraday electricity load data. I have quarter-hourly data for each day of the year. </p>
<p>In many countries daylight saving time is practive. This has the consequence that once a year a day is 1 hour longer (it has 25 hours) and once a year a day is shorter (only 23 hours). I don't think th... | 30,362 |
<p><strong>Background</strong>
I am comparing data on how ATPase activity from flight and leg muscle from locusts reacts to different concentrations of calcium. I plotted a scatter graph of each data set on the same graph (ATPase activity on the Y axis, calcium concentration on the X axis) and have a trend line for eac... | 69,754 |
<p>I have a set of data to analyze and I would welcome some ideas.</p>
<p>I have a series of indepedent observations when a call was produced by individuals. Each observation includes the ID of the caller, and information about other individuals in the vicinity (is there an ally? is there a friend?). There are about 4... | 30,363 |
<p>To build a SVM-based classifier, I have a training data set consisting of N data points. Some of them are redundant. For instance, there have 50 data points which are exactly the same, and there have other 100 data points which are exactly the same. I have two choices, remove the redundant ones and construct the red... | 69,755 |
<p>Suppose I have a quadratic regression model
$$
Y = \beta_0 + \beta_1 X + \beta_2 X^2 + \epsilon
$$
with the errors $\epsilon$ satisfying the usual assumptions (independent, normal, independent of the $X$ values). Let $b_0, b_1, b_2$ be the least squares estimates.</p>
<p>I have two new $X$ values $x_1$ and $x_2$... | 40,690 |
<p>We are trying to create auto-correlated random values which will be used as timeseries. We have no existing data we refer to and just want to create the vector from scratch.</p>
<p>On the one hand we need of course a random process with distribution and its SD.</p>
<p>On the other hand the autocorrelation influenc... | 30,365 |
<p>Following up on <a href="http://stats.stackexchange.com/questions/28338/how-to-evaluate-quality-of-probability-estimator-for-bernoulli-experiments">"How to evaluate quality of probability estimator for Bernoulli experiments?"</a>, I want to visualize the quality of an estimator for probability forecasting using a <a... | 69,756 |
<p>A colleague just asked me this question:</p>
<h3>Context:</h3>
<p>A psychological study had</p>
<ul>
<li>2 <code>group</code>s of participants (between subjects)</li>
<li>4 <code>context</code>s (within subjects))</li>
<li>each participant provided a <code>response</code> in each of the four contexts</li>
<li>th... | 40,693 |
<p>Consider a conjugate prior in the k-parameter canonical exponential family:</p>
<p>$$p(w|n_0,y_0)=c(n_0,y_0) \exp(n_0(y_0 w'-b(w)))$$</p>
<p>where $n_0>0, y_0 \in Y$ is the pseudo observation vector, $Y$ is an open subset of $\mathbb{R}^k$. I have to prove that the normalization constant $c(n_0,y_0)$ goes t... | 69,757 |
<p>I hope you can
help me with a question regarding calculating mean age from grouped census data. If the
age categories used were [0–4], [5–9], [10–14], and [15–19] years,
how would you calculate the midpoints? I initially assumed the midpoints would be 2, 7,
and so on. </p>
<p>However, I read in a worked example t... | 31,455 |
<p>First, let me say that I am a bit out of my depth here, so if this question needs to be re-phrased or closed as a duplicate, please let me know. It may simply be that I don't have the proper vocabulary to express my question.</p>
<p>I am working on an image processing task in which I identify features in an image, ... | 37,876 |
<p>I am not that familiar with statistics and was wondering about the best way to quantify the difference between a set of data and a function.</p>
<p>My scenario is that I have a set with maximum heart rate data from around 60 people, with their age. I'm trying to see which of all "mathematical models" out there that... | 69,758 |
<p>I'm trying to describe the equation in the attached screenshot in my own words. </p>
<p>$\lvert(\overline\chi_1-\overline\chi_2)\rvert > s_1(t_{1 @ 99 \%}) + s_2(t_{2 @ 75 \%})$</p>
<p>The equation tests whether 99% of population 1 lies outside of 75% of population 2. The equation is taken from Donegan, T., 201... | 69,759 |
<p>I'm working with multiple time series signals ${\{X_i\}}$ and one method to remove suspected noise is with PCA. But unlike most methods which remove the components with least variance, we remove much more substantial components (often the second or third). This is often done because empirically it's been shown to ... | 37,637 |
<p>I have repeated (x4) measurements on 90 subjects. The outcome is zero inflated.</p>
<p>The model output gives these estimates:</p>
<pre><code>Coefficients:
Estimate Std. Error z value Pr(>|z|)
(Intercept) -2.2151 1.6998 -1.30 0.193
time ... | 69,760 |
<p>I want to know if I need to use ARCH/GARCH model for my time series. How can I use <code>McLeod.Li.test</code> in R to do that and how should I interpret the result? the description in R help was not clear for me because in the example of the R help they used difference of the log of the time series and I do not kno... | 30,372 |
<p><strong>How do I work out an adequate/representative sample in the following scenario?</strong> </p>
<p>My intention is to use correlation and regression models to test the relationship between income level and money spent on a particular product by store type.</p>
<p><strong>Scenario</strong></p>
<p>There are 20... | 69,761 |
<p>I've read several articles about how to perform Weibull distribution but they all did it with wind speed data in a time series manner (example: recorded data every 10mins and then averaged to every hour). My prob is that I've got only mean monthly wind speed for a year (from January to December). So how should I dea... | 69,762 |
<p>Suppose that we have two sets of variables $\textbf{X}$ and $\textbf{Y}$. Let $$ \textbf{X} = \begin{pmatrix} X_1 \\ X_2\\ \vdots \\X_p \end{pmatrix}$$ and $$ \textbf{Y} = \begin{pmatrix} Y_1 \\ Y_2\\ \vdots \\Y_q \end{pmatrix}$$ </p>
<p>where $p \leq q$. </p>
<p>Define the following linear combinations: $$U_i = a... | 69,763 |
<p>I'm performing correlations between growth variables (e.g. debt growth and net income growth) and the correlation is rather strong. Nevertheless, I was wondering why when I perform the same correlation for debt growth and net income (e.g. net income 2008), so not comparing growth and growth I don't get any correlati... | 69,764 |
<p>I'm analyzing a data base from an ecological study and I'd like to read a good reference book about this kind of studies as there are some limitations concerning their analysis; for example, they are susceptible to ecological fallacy.</p> | 69,765 |
<p>I want to estimate covariance of a multivariate normal distribution from data using a Bayesian method. I want to force the result to be tridiagonal. I am looking for an appropriate prior or method. Is there any prior or method for this?</p> | 69,766 |
<p>It is common practice in psychology to add together ordered items to sum-scores, and then use these sum-scores for subsequent statistics. This is usually done without explicitly mentioning measurement level, and I guess people simply assume items to be interval or ratio. </p>
<p>I wonder about this practice, and th... | 30,377 |
<p>I have a large data set consisting of ca. 40 categorical data items and a few interval data items (real numbers, less than 5 such items). Most categories should have a lot of values that repeat themselves over and over and very few that appear very rarely. Some categories are also overcategories of others (like coun... | 69,767 |
<p>Given data $(x_{1}, y_{2}),..., (x_{n}, y_{n})$, consider the simple linear regression model $E(Y | X=x) =3.2 + B_{1}x, Var(Y|X=x)=\sigma^{2}$. Construct a 95% confidence interval for $B_{1}$. </p>
<p>I know that we first have to estimate the $\sigma$, but I was told that the degrees of the confidence interval is n... | 69,768 |
<p>Does anyone know of literature describing methods for generating synthetic data from a graphical structure that has been learned from observations of real data? The graph, depending on the type of data or the questions being asked of it, could be bipartite (as in topic modeling), or directed (as in a link graph-type... | 30,378 |
<p>I'm working with cluster-correlated data (individuals nested into households). I would like to modify the bootstrap sampling process to make a household-level bootstrap instead of the subject-level bootstrap. </p>
<p>My aim is to ensure that the entire household is included in the sample used to grow each tree of t... | 69,769 |
<p>I'm trying to solve the following issue :
Let's say that I have three normal random variables a,b,c, non correlated.</p>
<p>Let's say that I only have two observations of these, M and N where :</p>
<pre><code>M = a + b
N = a + c
</code></pre>
<p>And another variable I'm trying to explain :</p>
<pre><code>R = a +... | 30,379 |
<p>I am trying to run a sensitivity analysis on an efficiency indicator: the ratio between nitrogen outputs (milk, meat, crops) and nitrogen inputs (fertilizers, cattle feed, symbiotic fixation…). </p>
<p>I have 4 output variables and 12 input variables. However, they are not independent. For instance, fertilizer inpu... | 30,380 |
<p>I have a histogram of wind speed data which is often represented using a weibull distribution. I would like to calculate the weibull shape and scale factors which give the best fit to the histogram.</p>
<p>I need a numerical solution (as opposed to <a href="http://www.weibull.com/LifeDataWeb/probability_plotting.ht... | 69,770 |
<p>In my study, I have one group encoding 2 different types of words (within subjects) and 3 different dependent measures namely recall, recognition, rating. </p>
<p>I think that I can conduct repeated measure analysis.
But I am confused about what should I write for factor name. I think I have one factor with two lev... | 69,771 |
<p>If I have two players that are about to engage in a head to head competition, how do I simulate a winner based only on win percentage?</p>
<p>One idea I had was to create a "weighted winning pool" where I add the two percentages and then randomly pick a number in that pool. If it's in the percentage range of a team... | 40,713 |
<p>I am asked to give a lecture on clustering algorithms for an audience that is not very technical. With that in mind, I wanted to do a simple exercise where I will ask the audience to identify groups from a dataset. However, I cannot find good datasets that could be usable for this purpose.</p>
<p>Is there a dataset... | 37,812 |
<p>I'm trying to find the variance of $L$, $Var(L)$, using the delta method (I want to find a closed form). $L$ is defined as:
$$L = \frac{A}{B} + \frac{C}{D}$$
All $A$, $B$, $C$, and $D$ are dependent.</p>
<p>But I'm not sure how to proceed. </p> | 30,385 |
<p>I computed a simple linear regression model from my experiment measures in order to make predictions. I have read that you should not calculate predictions for points that depart too far from the available data. However, I could not find any guidance to help me know how far I can extrapolate. For example, if I calcu... | 49,566 |
<p>After I installed Graphviz, I used the following command to plot a tree resulting from a tree-structured analysis of my sequences: </p>
<p><code>> seqtreedisplay(mytree, filename=mytree, seqdata=mysequences, type="I", border=NA)</code> </p>
<p>However, I had this error message: </p>
<blockquote>
<p>'dot' ... | 69,772 |
<p>What i am trying to do is to take a machine learning algorithm that is already trained.Run the algorithm several times and collect the output.</p>
<p>Conduct a statistical analysis on the output and try to create an inference regarding the parameters of the algorithm </p>
<p>Is this possible ? Are there known stat... | 69,773 |
<p>If $a$ and $b$ are both independent, identically distributed normal random variables, what is the distribution of $\phi = \arctan{(-\frac{b}{a})}$? It is uniform, across $0$ to $2\pi$, but I am trying to see why. $a \sim \mathcal{N}(0,\sigma^2)$ and $b$ is identically distributed and independent to $a$.</p>
<p>For ... | 49,835 |
<p>Let $Y_1,Y_2,...,Y_n$ denote a random sample from the probability density function
$$f(y| \theta)= \begin{cases} ( \theta +1)y^{ \theta}, & 0 < y<1 , \theta> -1 \\ 0, & \mbox{elsewhere}, \end{cases}$$</p>
<p>Find an Estimator for $\theta$ by using the method of moments and show that it is consist... | 69,774 |
<p>I would like to use the <code>tune()</code> function in R to specify the hyperparameters in an SVM model. The particular SVM implementation that I am using is the one that is provided in the <code>e1071</code> package. </p>
<p>By default, <code>tune()</code> runs a K-fold cross-validation, and chooses the testing a... | 69,775 |
<p>I am plotting a residual plot to test for heteroskedasticity. The Breusch-Pagan test is significant and therefore I am suspecting there is evidence on heteroskedasticity. The question is:</p>
<p>(a) How can I interpret such graph? I know some points seem to be on top of each other etc. is it as simple as that?</p>... | 69,776 |
<p>If nonparametric tests are assumed to have less power than their parametric alternatives, does this imply that if any parametric test does not reject null, then its nonparametric alternative does not reject null too? How can this change if assumptions of parametric test are not met and the test is used anyway?</p> | 329 |
<p>As I know the standard linear equation has the following form in $R^2$:</p>
<p>$w_1 x_1 + w_2 x_2 = b$ where $b$ is the intercept with $x_2$</p>
<p>Also I know that a decision boundary in $R^2$ for a perceptron is a line. However I read everywhere that the decision boundary equation is the following:</p>
<p>$w_1 ... | 69,777 |
<p>Given an (observed) time-series $X_t$ with $X_t\in\{1,...,n\}$, is there a statistical test for testing the null-hypothesis that $P(X_t|X_{t-1},X_{t-2},...,X_1)=P(X_t|X_{t-1})$ (i.e. the markov-property)?</p> | 69,778 |
<p>I have a few questions about generalizations of the CLT and stable distributions. I'm trying to correct my understanding and make it precise. Please forgive my naivete, I am not a professional statistician :-)</p>
<p>If I take the sum of a large enough sequence of independent R.V.'s, do they always converge to a st... | 40,724 |
<p>I'm performing dimension reduction on some data sets and would like to evaluate how has a particular dimension reduction algorithm performed in terms of how much data is lost. If we are given 1000 dimensions, and we reduce it to 2, then how effective is it? I'm trying to figure till what should you do DR such that y... | 45,405 |
<p>I'm trying to make a video about loaded dice, and at one point in the video we roll about 200 dice, take all the sixes, roll those again, and take all the sixes and roll those a third time. We had one die that came up 6 three times in a row, which is obviously not unusual because there should be a 1/216 chance of th... | 69,779 |
<p>Is there any information out there about the distribution whose $n$th cumulant is given by $\frac 1 n$? The cumulant-generating function is of the form
$$
\kappa(t) = \int_0 ^ 1 \frac{e^{tx} - 1}{x} \ dx.
$$
I've run across it as the limiting distribution of some random variables but I haven't been able to find any... | 69,780 |
<p>I realise this is one of those "Don't start from here" type questions, and I did indeed tell them not to "start from here" but it would be a shame to junk the data.</p>
<p>Basically I have some interval normal data, Likert scale type stuff, from two groups, at time one and time two, and I know that some subjects in... | 69,781 |
<p>I have to verify some results. I have only the mean and its st. error, not the raw data. In a research paper they did a paired t test. Is it possible to check whether their p value is right by only using the means, st. errors and N, in SPSS or GraphPad?</p> | 69,782 |
<p>For $a_1,a_2$ and $b_1,b_2$, $\in\Re^+$, if $a_1<b_1$ , then for any perturbation by a random variable $\epsilon\in \Re^+$,
$$r_1=\frac{a_1+\epsilon}{b_1+\epsilon}>\frac{a_1}{b_1} $$ and if $a_2>b_2$, $$r_2=\frac{a_2+\epsilon}{b_2+\epsilon}<\frac{a_2}{b_2} $$</p>
<p>If $\epsilon$ is generated from a de... | 42,209 |
<p>If I am selecting 232 people from a pool of 363 people without replacement what is the probability of 2 of a list of 12 specific people being in that selection?</p>
<p>This is a random draw for an ultra race where there were 363 entrants for 232 spots. There is an argument about whether the selection was biased aga... | 49,438 |
<p>Let's say I have two signals $x_1$ and $x_2$, each having $N$ samples, i.e.:</p>
<p>$$ x_1 = \{ x_{11}, x_{12}, ..., x_{1N} \} $$
$$ x_2 = \{ x_{21}, x_{22}, ..., x_{2N} \} $$</p>
<p>The signals are both zero-mean. (Each signal's mean has already been subtracted from all of that signal's elements.)</p>
<p>Since ... | 30,402 |
<p>I previously asked this on StackOverflow, but it seems like it might be more appropriate here, given that it didn't get any answers on SO. It's kind of at the intersection between statistics and programming.</p>
<p>I need to write some code to do PCA (Principal Component Analysis). I've browsed through the well-kn... | 40,735 |
<p>I have a dataset of various ecological variables on which I want to run linear regression. The variables are continuous, but also include aspect data (sun exposure), in grades. My problem is that the aspect values ranges from 0 to 400, with 0=400=north. How can I include "cyclic" values in the regression? Should I k... | 69,783 |
<p>I'm currently working on cleaning/preprocessing a bunch of survey data from a collection of similar but distinct surveys. In order to combine the survey results this involves, among other things, identifying common (as in shared) questions (which might, obviously, not be identically phrased).</p>
<p>While the data ... | 30,404 |
<p>I have a real estates' condos sold dataset with the following fields </p>
<ol>
<li>DOM: Date on the market</li>
<li>sellPct: Percentage difference between the original and final price.</li>
<li>other fields such as Exposure( S,E,N,W), Parking (Yes,No), number of rooms,...</li>
</ol>
<p>I am trying to combibe DOM ... | 48,986 |
<p>I am a beginner with LASSO.
Is there any way (paper/code) to perform a LASSO type model in which only some of the explanatory variables are regularized? Or imposing different regulation parameters to several explanatory variables groups?</p> | 69,784 |
<p>There exists an option corr.bias for making regression analyses with the R package randomForest. The manual warns “Experimental. Use at your own risk.” What does corr.bias precisely do and why can it be dangerous to use it? As far as I know the bias correction is based on a linear regression between the out-of-bag-p... | 30,406 |
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