question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>Suppose that I have a random variable $X_1$ which is normally distributed, and a random variable $X_2$ having the density function shown in the figure below. How would I determine ${\rm P}(X_1 \le X_2)$? </p>
<p><img src="http://i.stack.imgur.com/ci1mv.jpg" alt="enter image description here"></p> | 70,903 |
<p>I want to perform regularized canonical correlation between two matrices with more variables than observations (same subjects), one of which is very large (~18000 columns). The only r package that could handle the matrix dimension was PMA (tried mixOmics, RGCCA...).</p>
<p>The problem is that the output of the func... | 70,904 |
<p>I am dealing with a real world problem and just wanted to check if I am going about this the right way. I have the probabilities that</p>
<ul>
<li>a defect will grow within a particular structure, say ${\rm P}(X_1)$</li>
<li>a person will be able to detect a defect, say ${\rm P}(X_2)$.</li>
</ul>
<p>These are two ... | 32,100 |
<p>I have this problem which I can't fully understand it:</p>
<blockquote>
<p>Assume you have entered in a foreign city of unknown size. At entrance
you see a tramcar with number $100$. Let us assume that the tramcar
lines of the city are numbered with integers starting from one, and
that every line has an equ... | 70,905 |
<p>According to <a href="http://nlp.stanford.edu/IR-book/" rel="nofollow">Manning et al.</a> (p. 155) <strong>accuracy</strong> is the sum of the diagonal in the confusion matrix divided by the sum of all items. On the other hand, following <a href="http://www.aclweb.org/anthology-new/J/J08/J08-4004.pdf" rel="nofollow"... | 70,906 |
<p>I am a beginner on statistic but come across an urgent situation that I have to work with statistics of stock prices data.</p>
<p>I have learned that ones can do a hypothesis test that rejects the Random Walk hypothesis in order to show that the data have trends. I have tried to understand it but that seems impossi... | 32,108 |
<p>So I've been playing around with SVMs and I wonder if this is a good thing to do:</p>
<p>I have a set of continuous features (0 to 1) and a set of categorical features that I converted to dummy variables. In this particular case, I encode the date of the measurement in a dummy variable:</p>
<p>There are 3 periods ... | 70,907 |
<p>I have a 2-class problem involving many features. Does a linear support vector machine (SVM) classifier only take into account the values of these features and nothing more? Does it see the relationships between the variables? For example, does it work like this: if feature number 80 is "0", then feature 2: needs to... | 49,386 |
<p>I have put a question on here before re SEM and small sample sizes. I have 3 factors each with 3 manifest variables each. I only have 90 records. I want to find out the amount of covariance between the factors AND between ALL the manifest variables. I also want to determine whether the 3 factors predict a forth perf... | 70,908 |
<p>I am reading through the <a href="http://courses.cs.washington.edu/courses/cse312/11wi/slides/12em.pdf" rel="nofollow">EM-Algorithm</a> but on the slide 39, I don't get how </p>
<p>$$P(D) = P(D|A)P(A) + P(D|B)P(B)$$</p>
<p>I am trying to understand it in order to get my head around modelling with mixture of Gaussi... | 32,112 |
<p>Regarding the standard DID model:
$$
y=\alpha+\beta_1\text{treat}+\beta_2\text{post}+\beta_3\text{treat⋅post}+u
$$
What exactly does it mean if say $\beta_3$ is not statistically significant, but $\beta_1$ is? Does the significance of $\beta_1$ just mean that my control group and my experimental group differed in th... | 42,792 |
<p>I have a model for predicting multiple count variables (multivariate count regression) given some covariates. Are there any publicly available datasets I could experiment with?</p> | 32,113 |
<p>Suppose that we choose the size of the test to be $\alpha = 0.05$, and based on our sample size $n$ and magnitude of the absolute value of the estimate, we determine that the test's power (i.e., 1 - Prob(Type 2 Error)) is $99.9\%$. </p>
<p>If I then fail to reject $H_0=0$ against $H_a \not= 0$, what consequences do... | 42,794 |
<p>How to find the median (or approximate median) of n chunks of values. The values in each chunk can be assumed to have been sorted if it helps. In addition, the existence of a histogram for each chunk is allowed.</p> | 32,114 |
<p>I have observed the historical PE (price / profit) value of a stock and realized that it roughly follows a log normal distribution. However, even when the next earning data point is easily predictable, this distribution cannot be used to predict the distribution of next stock price data point, because, the next PE v... | 70,909 |
<p>I want to run a gdp vs. oil consumption model where oil consumption is suspected to be endogenous - correlated with the error terms. Can a variable correlated with world oil price but not with the gdp of the country of interest be a valid instrument? </p> | 70,910 |
<p>Suppose that I fit a Bayesian multinomial logistic regression model where the dependent categorial variable indexes $x$ groups, and the predictors are the same across groups. I now have $x - 1$ sets of $p$ regression coefficients and want to compare the regression coefficients of one of the groups to the two others.... | 70,911 |
<p>In their 1989 paper "<a href="https://www.dropbox.com/s/deo5u3jfgko7q6a/rosnow_1989_PB.pdf" rel="nofollow">Definition and Interpretation of Interaction Effects</a>", Rosnow & Rosenthal write:</p>
<blockquote>
<p>When interaction is claimed in a factorial arrangement, the results
almost always require more d... | 70,912 |
<p>I have an i.i.d. sample with this density:</p>
<p>$ f_\theta (x) = k * exp (- (x - \theta)^4 ) $</p>
<p>How can I obtain the sufficient statistic?</p>
<p>Is the statistic that I find also complete?</p>
<p>Thank you very much!</p> | 70,913 |
<p>I am not a mathematician. I have searched the internet about KL Divergence. What I learned is the the KL divergence measures the information lost when we approximate distribution of a model with respect to the input distribution. I have seen these between any two continuous or discrete distributions. Can we do it be... | 70,914 |
<p><strong>Why I think I need to fit a constrained natural spline</strong></p>
<p>I'm working with IBI (interbeat intervals). The measured IBI's include some invalid values. I'm working on an imputation algorithm to impute for the invalid IBI's. Suppose I have an interval with 5 invalid IBI's. Part of my idea on imput... | 32,118 |
<p>What I am looking to do is test for a correlation between an activity (in this case nesting) with cumulative rainfall from the previous two weeks. For example, say one individual nested on DayX where the total rainfall from the previous 2 weeks is 4cm and another individual nested on DayY with 8cm of prior rain, and... | 70,915 |
<p>I have just started to study Estimation theory and following the book "Fundamental of Statistical Signal Processing" by Steven M. Kay Vol 1. Most of the examples are based on the assumption that data follows a Gaussian distribution. COnsider, the example of estimating an unknown parameter $A$ from the relation: $x[n... | 5,490 |
<p>I have the following state-space model:
$$\begin{aligned}
y_t&=c+Ax_t+q_t, &q_t \sim \mathcal N(0,Q), \\
x_t&=\mu+Bx_{t-1} + v_t, &v_t \sim \mathcal N(0,R),
\end{aligned}
$$
where the series $x_{t=1}^T$ is latent.</p>
<p>I am interested in estimating $\Phi=[ x_{t=1}^T, A,B,R,Q,c,\mu ]$ via Bayesian... | 32,121 |
<p>How do I interpret the coefficient for the spatially lagged dependent variable in the spatial lag model or spatial autoregressive model (SAR) (y = αιn + ρWy + Xβ + ε) and how do I interpret the coefficient of the spatially lagged dependent variable and the coefficients of the spatially lagged independent variables i... | 32,122 |
<p>It seems that KNN is a discriminative learning algorithm but I can't seem to find any online sources confirming this.</p>
<p>Is KNN a discriminative learning algorithm?</p> | 70,916 |
<p>I've got a bunch of data on pop singers' performance on the Hot 100 charts over time, and I'm trying to compare the early part of different artists' careers. For example, I might look compare Miley Cyrus' career to the commensurate period of Cher's career:</p>
<p><img src="http://i.stack.imgur.com/3XWQb.png" alt="e... | 19,656 |
<p>Consider an offset term in a Poisson regression:</p>
<p>$$\log \mu_x = \log t_x+ \beta_0 + \beta_{1} x$$</p>
<p>To interpret $\beta_0$, would you need to consider $(\beta_0+ \log t_x)$? Because what if $t_x \neq 1$? Is the interpretation of $\beta_0$ the mean number of events when $t_x = 1$ and $x=0$? Suppose $t_1... | 70,917 |
<p>Reading a paper, the authors use a "Conditional fixed effects Poisson with population exposure." I wasn't sure what "population exposure" meant, so I looked it up. It seems like the term comes from epidemiology (not my field). Could I check to see if I've understood it correctly?</p>
<p>Poisson models try to estima... | 32,098 |
<p>Suppose I know the mean and standard deviation of a (roughly) normally distributed variable x. Is there any way for me to calculate the mean and standard deviation of f(x)?</p>
<p>The particular problem I am working with involves needing to find the mean and standard deviation of sine and cosine of variables whose ... | 70,918 |
<p>Just wondering what are the advantages of using one over the other. I'm just looking for some general answers here.</p>
<p>For starters:
<li>VB gives a guaranteed lower bound for the likelihood. </li>
<li>EP is faster? VB has quite a lot of iterations till convergence, unless someone came up with a faster method.</... | 70,919 |
<p>I have some survey data collected from 15 government organizations. Using this data, I would like to run an OLS regression to estimate the influence of variables x1 and x2 on y. I have run two models: one including 14 dummy variables accounting for potential differences from organizational membership, and one not in... | 70,920 |
<p>Let $A_1, A_2, \ldots$ be independent random variables with known distributions. </p>
<p>I'm wondering if it's possible to equivalently decompose the probability above into separated constraints?<br>
For example:<br>
\begin{align*}
\Pr(A_1 < b_1) & > 1-p_1 \\
\Pr(A_2 < b_2) & > 1-p_2 \\
&..... | 70,921 |
<p>I need to convert images into vectors (image vectorization). I have 165 images in total, divided into 15 subjects of 11 images each.
Following is code i have written to convert images into vectors. </p>
<pre><code> no_of_images = 165;
class=dir('<path of the images>*.pgm');
for i=1:length(class... | 70,922 |
<p>I am trying to generate a simulated data matrix that is correlated by both observation and variable directions. So far I know how to do this for <strong>variable x variable</strong>. </p>
<p><img src="http://i.stack.imgur.com/NgP8j.jpg" alt="enter image description here"></p>
<pre><code> # correlated matrix betwee... | 70,923 |
<p>Is this simplistic way of describing GARCH processes correct: </p>
<blockquote>
<p>Future prices do not depend on previous prices per se, but rather on the previous variance.</p>
</blockquote>
<p>If this is incorrect, is there a model that does this?</p> | 32,128 |
<p>I would like to estimate the constant in MA(1) process using LSE, but am finding it very difficult. </p> | 70,924 |
<p>I am trying to predict species presence or absence using randomForest in R (classification). In fact, I am trying to do it for several species, in separate models. </p>
<p>For a couple of the species, the training data are quite unbalanced e.g., 70 observations of species presence, and and 6500 observations of spec... | 268 |
<p>I have a model of an $\mathrm{AR}\left(2\right)$ process, thus:</p>
<p>$X_n + a_1X_{n-1}+a_2X_{n-2}=Y_n \qquad \mbox{for} \qquad n=0,\pm1,\pm2,\ldots $</p>
<p>and I have the equivalent stochastic differential equation in Continuous Time:</p>
<p>$\ddot{X}\left(t\right)+\alpha_1 \dot{X}\left(t\right) + \alpha_2 X\l... | 70,925 |
<p>I need to estimate a truncated gamma distribution parameters (shape , scale).</p>
<p>But, I only know the data mean and std. dev. I do not know the data set.</p>
<p>Given the mean and std. dev. of a data set from a truncated gamma distribution, how to find shape and scale of the distribution parameters ?</p>
<p>I... | 70,926 |
<p>I am reading an internal paper at my university that refers to volatility (for a variable not explicitly mentioned) as:</p>
<p>$\langle X,X\rangle = \int_0^T \sigma_t \, \mathrm{d}t.$</p>
<p>I am unfamiliar with expectations using this notation with commas, and subsequent uses do not indicate inner products, inner... | 6,162 |
<p>Suppose I have a procedure to select K features out of M. I repeat the procedure N times on, say bootstrapped datasets, and count how many times feature #1 appeared among selected, denote k1, how many times feature #2 appeared, denote k2, etc. </p>
<p>Question 1: What would be a suitable statistical test to check f... | 70,927 |
<p>In SVM (linear kernel) classification analyses of a data-set of gene expression (~400 variables/genes) for ~25 each of cases and controls, I find that the gene expression-based classifiers have very good performance characteristics. The cases and controls do not differ significantly for a number of categorical and c... | 70,928 |
<p>What does it mean for a study to be over-powered? </p>
<p>My impression is that it means that your sample sizes are so large that you have the power to detect minuscule effect sizes. These effect sizes are perhaps so small that they are more likely to result from slight biases in the sampling process than a (not n... | 70,929 |
<p>Assume you are given two objects whose exact locations are unknown, but are distributed according to normal distributions with known parameters (e.g. $a \sim N(m, s)$ and $b \sim N(v, t))$. We can assume these are both bivariate normals, such that the positions are described by a distribution over $(x,y)$ coordinate... | 49,475 |
<p>I am monitoring variability in sentencing outcomes (custodial sentence length) amongst matched groups. The aim is to determine whether sentence variability went up or down after a policy was implemented.</p>
<p>I have about 40 groups of sentences, which are matched on the characteristics of the case. For exampl... | 70,930 |
<p>Suppose $X_1,\ldots,X_n$ is a random sample of distribution $f(x|\theta)=\theta (1-\theta)^x,x=0,1,2,\ldots\ ,0<\theta<1$. </p>
<p>How can I calculate Bayes estimator of parameter $\gamma(\theta)=\frac{1-\theta}{\theta}$ under loss function $L(\theta,\delta)=\displaystyle\frac{\theta^2}{1-\theta}(\delta-\the... | 70,931 |
<p>I'm new to statistics and R. So, I have a dataset on which I want to build a predictive model.</p>
<p>Since there is quite a variability in the input variables, I thought it would be better to cluster my data first (using kmeans) and then build separate models on each cluster (e.g. Random Forest). Using 10-fold cro... | 70,932 |
<p>I am trying to solve for the parameters in the maximum entropy problem in R using the nonlinear system:</p>
<p>$\ \int_l^u e^{a+bx+cx^2}dx=1$</p>
<p>$\ \int_l^u x e^{a+bx+cx^2}dx=\mu$</p>
<p>$\ \int_l^u x^2 e^{a+bx+cx^2}dx=\mu^2+\sigma^2$</p>
<p>where $l$ and $u$ represent the lower and upper bound on the suppor... | 70,933 |
<p>You are given a "blackbox":</p>
<p>$RSS = (Y - X\beta)'(Y-X\beta)$</p>
<p>for any linear model $Y=X\beta+\epsilon$</p>
<p>You have $n=60$ observations, and two predictor variables. You want to test </p>
<p>$H_0: \beta_1 = \beta_2$ in the model:</p>
<p>$Y = \beta_0+\beta_1X_1+\beta_2X_2+\epsilon$</p>
<p>Descri... | 32,137 |
<p>I have some set of measurements that I have represented as vectors $x^t$ for $t \in \{ 1, 2, ...\}$.</p>
<p>I want to test "convergence" of the process (visually) in some sense.</p>
<p>I thought maybe I could run PCA on $x^t$ and then plot the projections to the first principal component, 2nd, etc... and see wheth... | 70,934 |
<p>I am new to the topic of copulas and my math is limited. I have different questions:</p>
<p>1.
Is it correct to say, that
$C: [0,1]^d \rightarrow [0,1]$ is a mapping from a multidimensional distribution to its one dimensional margins? Or that this is a mapping from the unit cube to the uniform margins?</p>
<p>2.
I... | 5,670 |
<p>To test the goodness-of-fit in generalized linear models with parameter $\beta$, from <a href="http://www.biostat.umn.edu/~xianghua/8452/note/05GEE.pdf" rel="nofollow">a note</a></p>
<blockquote>
<p>Another measure of discrepancy is the generalized Pearson’s chi-square statistic
$$\sum_{i=1}^m \frac{(y_i − \hat... | 70,935 |
<p>In principal components analysis, the first $k$ principal components are the $k$ <em>orthogonal</em> directions with the maximum variance. In other words, the first principal component is chosen to be the direction of maximum variance, the second principal component is chosen to be the direction orthogonal to the fi... | 32,143 |
<p>Looking at a between-groups ANOVA situation, what do you get by actually doing such an ANOVA test first, and second do post-hoc (Bonferroni, Šidák, etc.) or planned comparisons tests? Why not skip the ANOVA step entirely? </p>
<p>I gather that in such a situation, the one benefit of between-groups ANOVA is to being... | 70,936 |
<p>500 patients had an operation to remove stomach cancer. There exists a clinical guideline that suggests that a minimum of ten lymph nodes should be removed during the operation. I am therefore interested in the proportion of patients who had at least ten nodes removed. The variable <code>Fewer_or_more_than_ten</code... | 70,937 |
<p>Let's say I got a reading of 5 for a given measurement.</p>
<p>For a random population, I got the following dataset of readings: </p>
<pre><code>random <- c(2,2,1,1,5,76,3,89,35,66,77,22,99,100,0,34,67,88,95)
</code></pre>
<p>I want to determine the probability of getting a reading equal or less than my readin... | 70,938 |
<p>I fitted a Bayesian logistic regression in WinBugs and it has an interaction term. Something like this:
$$\mathrm{Prob}(y_{i}=1) = \mathrm{logit}^{-1} (a + b_{1}*x_{i} + b_{2}*w_{i} + b_{3}*x_{i}*w_{i})$$</p>
<p>where $x$ is a standardized continuous variable, and $w$ is a dummy variable.
In reality the model is mo... | 70,939 |
<p>While im going through the derivation of E step in EM algorithm for pLSA, i came across the following derivation <a href="http://www.hongliangjie.com/2010/01/04/notes-on-probabilistic-latent-semantic-analysis-plsa/" rel="nofollow">at this page</a>. Could anyone explain me how the following step is derived. </p>
<p>... | 70,940 |
<p>I have measured the following variables on 200 individuals.</p>
<ul>
<li><p>Independent variables:</p>
<ul>
<li>Measures of personality
<ul>
<li>Extraversion</li>
<li>Conscientiousness</li>
</ul></li>
<li>Leader Member Exchange (LMX) quality</li>
</ul></li>
<li><p>Dependent variable</p>
<ul>
<li>Measures of sales... | 43,072 |
<p>In the paper of <a href="http://www.cs.brown.edu/~th/papers/Hofmann-UAI99.pdf" rel="nofollow">Probabilistic Latent Semantic Analysis</a> by Hofmann, the author fits the model for <em>document</em> $\times$ <em>word</em> matrix through EM Algorithm in section 3. I was able to follow the derivation and meaning of the ... | 70,941 |
<p>I am building a Box-Jenkins model in Excel using solver. The model is AR(2).
The data that I have contains trend and seasonality both. </p>
<p>I know how to remove seasonality using seasonal indexes and add it back to the forecast.
But, how do I handle trend? If I remove trend from the data, how should I add it ba... | 32,148 |
<p>I've got a question concerning the estimation of a tobit model with the <a href="http://cran.r-project.org/web/packages/AER/index.html" rel="nofollow">AER</a> package in R. I observed t-distributed residuals, so that the assumption of normal distributed std errors is violated. Fortunately it's possible to choose "t"... | 70,942 |
<p>Given a desired distribution over a set of finite states, I wish to construct a tridiagonal Markov chain that would have a stationary distribution same as the desired distribution.</p>
<p>The reason I want to do this is as follows. I have a linear sequence of blocks that an agent can traverse. Each time, the agent ... | 70,943 |
<p>When it comes to the training of a Hidden Markov Model using multiple training instances should I first take a single instance and train the model until the convergence and then move on to the next instance or should I use multiple instances sequentially to train the model?</p> | 70,944 |
<p>Population r-square $\rho^2$ can be defined assuming fixed scores or random scores:</p>
<ul>
<li><p>Fixed scores: The sample size and the particular values of the predictors are held fixed. Thus, $\rho^2_f$ is the proportion of variance explained in the outcome by the population regression equation when the predict... | 70,945 |
<p>I'm relatively familiar with the distinction between the terms statistic and parameter. I see a statistic as the value obtained from applying a function to the sample data. However, most examples of parameters relate to defining a parametric distribution. A common example is the mean and standard deviation to parame... | 70,946 |
<p>Say we are trying to predict occurrences of lightning bugs based only on the dates on which people reported seeing them. So climate change, weather, and other influencing factors are imaginary.</p>
<p>So there are $n$ recorded occurrences of lightning bugs. Since many people have contributed and the recording is no... | 32,151 |
<p>I have an example data set as follows:</p>
<pre><code>Volume <- seq(1,20,0.1)
var1 <- 100
x2 <- 1000000
x3 <- 30
x4 = sqrt(x2/pi)
H = x3 - Volume
r = (x4*H)/(H + Volume)
Power = (var1*x2)/(100*(pi*Volume/3)*(x4*x4 + x4*r + r*r))
Power <- jitter(Power, factor = 1, amount = 0.1)
plot(Volume,Power)
... | 70,947 |
<p>In <code>SPSS</code>, regression analysis yields two types of coefficients (standardized and unstandardized). What is a standardized coefficient in statistical sense?</p> | 49,859 |
<p>I am trying to find a name for the kind of study design/analysis I am working on so I can use it to look up best practices and examples of people who have done this kind of thing well.</p>
<p>Essentially I am trying to retrospectively compare two ways of taking biopsies of an organ. Since we are taking biopsies, we... | 70,948 |
<p>I can think of four ways to perform model selection <code>nlme</code>'s: <code>LRT</code>, <code>AIC</code>, <code>BIC</code> and <code>CV</code>. It would be much appreciated if anyone could add to/correct this list. I vaguely recall somebody computing <code>cAIC</code> in <code>SAS</code>, but not how df was defin... | 366 |
<p>I'm a grad student trying to absorb from the book Pattern Recognition and Machine Learning. However, I found that I really need a good grasp of matrix calculus before I can deduct the formulas myself (since I think in this way learning could be more effective). For example, when deducting Gaussian Mixture Model usin... | 70,949 |
<p>In "<a href="http://www.jstor.org/stable/2291267" rel="nofollow">Alternatives to the Median Absolute Deviation</a>" (Rousseeuw and Croux, <em>J. Amer. Statistical Assoc</em>, <strong>88</strong>(424), 1993, pp.1273–1283) and a few other papers from the same authors published in 1992–1993, Rousseeuw and C... | 70,950 |
<p>I'm wondering how to calculate precision and recall measures for multiclass multilabel classification, i.e. classification where there are more than two labels, and where each instance can have multiple labels?</p> | 32,156 |
<p>I would like to generate some artificial data to evaluate an algorithm for classification (the algorithm induces a model that predicts posterior probabilities).</p>
<p>These are some basic properties of the dataset:</p>
<ul>
<li>Features have to be continuous</li>
<li>Response variable is dichotomous (either 0 or ... | 32,157 |
<p>I am using Kalman Filter to estimate my state variables for a time series data. But all my parameters in KF are unknown.</p>
<pre><code>S(t) = A*S(t-1) + B*X(t) + Q ----------Sate process
Z(t) = H*S(t) + W*D(t) + R ----------Measurement process where,
T: the total number of time slots in the time series... | 5,774 |
<p>My question is about the DLM package and the dlmMLE.</p>
<p>Lest's say that I have a bivariate model of this kind:</p>
<p>$$Y(t)= Fb(t)+e(t)$$
$$b(t) = u + Gb(t) +w(t)$$</p>
<p>$$b(t)=(b_1(t),b_2(t)),\quad u = (u_1,u_2)$$
Rewriting the model in matrix notation, the state equation becomes:
$$d(t) = H d(t) +w(t),$$... | 70,951 |
<p>I have a question regarding a financial/statistical problem.</p>
<p>How do you calculate the variance of the outcome of an investment in a stock, when the investment is so called time diversified, i.e. spread out over time. </p>
<p>So, an investor invests an amount every month during 24 months in the same stock.
W... | 37,888 |
<p>I am a student in biology, currently finishing my master in Behavior, evolution and conservation. I have been in the Swiss national park for my field work and I have some trouble to analyze my data.</p>
<p>So basically what I have is a lot of factors and what I need to do is a multinomial logistic regression :</p>
... | 32,160 |
<p>I'm reading a paper by Max Kuhn called <a href="http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CDIQFjAA&url=http://www.jstatsoft.org/v28/i05/paper&ei=oj_IUK5FsMrQBdC-gcgF&usg=AFQjCNFNcBMI8dmK33j2Q1TPtmXLy4GUxA&bvm=bv.1354675689,d.d2k" rel="nofo... | 32,162 |
<p>I'm trying to implement a logistic regression function in matlab. I calculated the theta values, linear regression cost function is converging and then I use those parameters in logistic regression function as a decision boundary. </p>
<p>I'm trying to obtain an overfit logistic regression tree to show how cost fun... | 42,858 |
<p>I'm using the survival package in R to analyze clinical data. I am analyzing two different groups of patients, when I calculate survdiff in order to compare the curves, I got p= 0.135, but when I adjust the model using coxph and different covariates, let say clinical cancer stages, , I got an overall logrank score o... | 32,169 |
<p><strong>Context</strong></p>
<ul>
<li>you have 200 observations of an individual's running time for the 100 metres measured once a day for 200 days.</li>
<li>Assume the individual was not a runner before commencement of practice</li>
<li>Based on the observed data and the 199 other observations, you want to estimat... | 32,170 |
<p>Considering two Bayesian models:</p>
<ul>
<li>Poisson Likelihood & Beta Prior:</li>
</ul>
<p>$p(y|\lambda) \sim \text{Pois}(\lambda)$, $p(\lambda) \sim \text{Be}(a, b)$:</p>
<p>$$ p(\lambda|y) \propto \lambda^{a-1}e^{-b\lambda} \times \lambda^{y}e^{-\theta} $$</p>
<p>$$ = \lambda^{a+y-1}e^{-\lambda(1+b)} $$<... | 32,172 |
<p>The statistics book I am reading recommends omega squared to measure the effects of my experiments. I have already proven using a split plot design (mix of within-subjects and between-subjects design) that my within-subjects factors are statistically significant with p<0.001 and F=17.</p>
<p>Now I'm looking to s... | 70,952 |
<p>this is my first attempt at posting here. I looked through CrossValidated and found two similar problems without answers (see <a href="http://stats.stackexchange.com/questions/28869/how-to-combine-weka-classifiers?rq=1">How to combine WEKA classifiers</a> and <a href="http://stats.stackexchange.com/questions/32097/... | 70,953 |
<p><strong>Problem</strong></p>
<p>Let $X$ be a $n$-bit random variable and $s$ be the known estimated value for $X$. Our estimation has an error with normal distribution. In other words, $X|s \sim \mathcal{N}(s,\sigma_z^2)$.</p>
<p>We want to calculate $p\left(B_1(X)=1|s\right)$ numerically where $B_1(X)=1$ means t... | 42,868 |
<p>In response to <a href="http://stats.stackexchange.com/questions/24046/can-a-repeated-measures-design-be-non-temporal-in-nature">this</a> question, regarding whether my design where I randomly presented participants with pictures from different categories was an example where I should use a repeated measures ANOVA, ... | 32,178 |
<p>I have a dataset where all observations are measured several times and reported outcomes correspond to those measurements. In other words, my set of data points looks like</p>
<p>$\{x_i, y_{i_1}, y_{i_2}, ... y_{i_n}\}$</p>
<p>I would like to make a predictive model to predict $y$ from $x$. What should I try to pr... | 32,179 |
<p>I'm using the caret package at the moment to perform different forms of analysis on my dataset. I did the following to do 10-fold cross validation, 10 times:-</p>
<pre><code>>library(caret)
>cadets <- read.csv("pathway/CADETS.csv")
>ctrl <- trainControl(method = "repeatedcv", number = 10, repeats = 1... | 5,878 |
<p>According to Wikipedia the beta probability distribution has two shape parameters: $\alpha$ and $\beta$.</p>
<p>When I call <code>scipy.stats.beta.fit(x)</code> in Python, where <code>x</code> is a bunch of numbers in the range $[0,1]$, 4 values are returned. This strikes me as odd.</p>
<p>After googling I found o... | 70,954 |
<p>Hello I am trying to find a Matlab version of a function which performs best subset selection for least squares regression using leaps and bounds (branch and bound) approach. Like in the paper by Furnival and Wilson (1974)*.</p>
<p>The R equivalent of this is the <code>leaps</code> package.</p>
<p>Any suggestions ... | 5,879 |
<p>I am trying to use scikit-learn for polynomial regression. From what I read polynomial regression is a special case of linear regression. I was hopping that maybe one of scikit's generalized linear models can be parameterised to fit higher order polynomials but I see no option for doing that.</p>
<p>I did manage to... | 70,955 |
<p>Could anyone give me a hint on the following problem? Thanks!</p>
<p>Let $f$ be a random variable over a probability space $(\Omega,A,P)$. Show that</p>
<p>$f$ is integrable $\iff $ $\sum\limits_{k=1}^\infty P(\{|f|>n\}) < \infty.$</p>
<p>Note: Consider the sets $A_n:=\{n-1<|f|\le n\}$, $n\in \mathbb{N}$... | 70,956 |
<p>I've some data that I've clustered and calculate the similitude within my cluster centroids to spot which class centroids are close to which ones. My goal was to visualize this as a map of points. I thought that the best way was to represent the data as a complete graph where each node represent a centroid and the e... | 32,185 |
<p>Please first note that I do know about the central limit theorem but I wish to derive an exact expression for the sample mean for any continuous distribution with probability density function $f(x)$. I thought I derived it correctly here but there is some mistake I can't spot. Can anyone tell me where I have made a ... | 70,957 |
<p>I was looking at the formula for the conditional covariance of a partitioned matrix. I understand the intuition behind the equation for the conditional covariance, but I'm not sure how to show that the covariance matrix is positive definite.</p>
<p>$$\text{For }\bf{x} \sim N(\bf{\mu},\Sigma),$$</p>
<p>$$
\bf{x}=
\... | 70,958 |
<p>I have a set of distributions that are sampled. How do I measure their similarity between themselves or as a group/set?</p>
<p>So, given a finite domain for a sampled function$F_j(x)$, with $x_i \in {1,\ldots,N}$ and $j \in {1, \ldots, J}$. I would like a measure $\cdot(F_{1,J})$ for how similar the distributions a... | 70,959 |
<p>Consider such a task: I have the figures on last year's bookselling of a certain book store, and the information of the first half of this year too. Now I want to predict the figure at the end of this year. I've checked R's <code>forecast</code> package. But it seems to only work on a single time series each time. H... | 48,429 |
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