question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>This seems so elementary, but I always get stuck at this point…</p>
<p>Most of the data I deal with are non-normal, and most of the analyses based on a GLM structure. For my current analysis, I have a response variable that is "walking speed" (meters/minute). It's easy for me to identify that I cannot use OLS, bu... | 32,943 |
<p>I really hope I'm not asking this question on the wrong stackexchange site, but seen as this question has a lot to do with statistics I'm guessing I might be in the right place.</p>
<p>There are certain rules in medical statistics as I understand, for example results that show below 7% difference between the test g... | 71,480 |
<p>I am trying to cluster Facebook users based on their likes.</p>
<p>I have two problems: First, since there is no dislike in Facebook all I have is having likes (1) for some items but for the rest of the items, the value is unknown and not necessarily zero (corresponding to a dislike). If use 0 for unknowns, then I ... | 32,945 |
<p>I made a logistic regression model using glm in R. I have two independent variables. How can I plot the decision boundary of my model in the scatter plot of the two variables. For example, how can I plot a figure like:
<a href="http://onlinecourses.science.psu.edu/stat557/node/55">http://onlinecourses.science.psu... | 43,849 |
<p>I have gigabytes of time-series data stored in HDF5 files and while there is the very basic visualization tool available in HDFViewer, I'm interested in knowing if there are rich visualization (charting/graphing) tools available for working with time-series data stored in HDF5 files.</p>
<p>I know that the plethora... | 71,481 |
<p>I developed the ez package for R as a means to help folks transition from stats packages like SPSS to R. This is (hopefully) achieved by simplifying the specification of various flavours of ANOVA, and providing SPSS-like output (including effect sizes and assumption tests), among other features. The <code>ezANOVA()<... | 663 |
<p>Let's say I have a data set $X = [1,2,3,4,5]$. And I want to measure how close it is to a Gaussian distribution. Is there a way to use cross-validation to do this?</p>
<p>For example, if I do leave-one-out cross-validation, I could calculate the sample mean and variance for $2...5$, then calculate $P(1)$. I repe... | 71,482 |
<p>I have the model that I need to estimate, $$ Y = \pi_0 + \pi_1 X_1 + \pi_2 X_2 + \pi_3 X_3 + \varepsilon, $$
with $\sum_k \pi_k = 1 \text{ for }k \geq 1$ and $\pi_k\ge0 \text{ for }k \geq 1$. </p>
<p>Elvis <a href="http://stats.stackexchange.com/questions/21565/how-do-i-fit-a-constrained-regression-in-r-so-that-coe... | 71,483 |
<p>I'd like to run a grid search cross-validation on the probability outputs of the SVC classifier. In particular I'd like to minimize the negative log likelihood. Is this a reasonable thing to do? I'm doing it b/c the dataset is: a) imbalanced 5:1 and b) not at all separable i.e. even the "worst" observations have a ... | 71,484 |
<p>I'm working on an econometrics problem set, and I'm having some major problems computing asymptotic variance for this estimator. I'm considering a fixed-effects model </p>
<p>$$
Y_{it} = \beta_1 X_{it} + \alpha_i + u_{it}
$$</p>
<p>With $t=1,2$. Letting $\Delta Y_i=Y_{i2}-Y_{i1},\Delta Y_i=X_{i2}-Y_{i1},\Delta u_i... | 38,886 |
<p>Let $X_1$ and $X_2$ and Z denote independent, real valued random variables and
$$Pr(Z=0) = 1-Pr(Z=1) = \alpha$$ for some $0<\alpha<1$ Define</p>
<p>Y = $X_1 $ if $Z=0$</p>
<p>= $X_2$ if $Z=1$</p>
<p>(a) Suppose that $E(X_1)$ and $E(X_2)$ exist, does it follow that E(Y) exists?
(b) Assume that $E(|X_1|) <... | 32,958 |
<p>I'm trying to understand Bayesian Networks and am attempting to apply it to solve some problems in the world of marketing, most notably search engine marketing. I have a data on EACH in click to a website, the date/time, what keyword that visitor came from, how much I paid for that keyword, which ad was clicks, whet... | 32,960 |
<p>I was just wondering:</p>
<p>If the joint distribution of $X$ and $Y$ is independent with $Z$, does it imply that $X$ and $Z$ are independent as well?</p>
<p>Can anyone give a counterexample/proof? </p> | 71,485 |
<p>I am experimenting with developing a linear model <code>lmodel1</code> which predicts a <code>temp</code> response variable, given three independent variables <code>sea.distance</code>, <code>altitude</code>, <code>latitude</code>. <code>model1</code> is calculated as follows: </p>
<p><code>model1 <- lm(tempera... | 71,486 |
<p>I have some set of random data. I would like to check if this data constitute a time series. I know how to apply a simple moving average method to the data. But after applying it, how can I say if the data is time series or not?</p> | 49,924 |
<p>For my thesis, I have gathered search volume data (<code>svi</code>) from Google and message data from Twitter (<code>tweets</code> is the number of daily tweets) for serveral companies (<code>comp</code>). The variable <code>tradevol</code> is the trading volume in the stock of a company, as taken from Yahoo! Finan... | 71,487 |
<p>We just designed a text classification system, and now it's time for me to write up some of the results we got. We observed that our classifier tends to perform better if we exclude documents below a certain length ($L$ characters, say) so it has enough data to learn from and make judgments on, and I'm not sure how ... | 71,488 |
<p>I have run an experiment in which I measure the expression of a particular gene under three different medium conditions (neutral,ATPlo,ATPhi). We took samples who have two different genotypes for a particular SNP (AA,AG).
What I would like to show is that for samples with the AA genotypes the medium has an effect on... | 12,334 |
<p>I'm a bit stuck on running a GLM between 3 continuous variables in <strong>R</strong>. I can't make them categorical as it removes the significance. I have two questions. </p>
<p>I'm analysing data on eggs.</p>
<p>I had read that you could control for variables by adding them in using <code>+</code> like so:</p>
... | 36,658 |
<p>I wonder if there is any statistical test to "test" the significance of a bimodal distribution. I mean, How much my data meets the bimodal distribution or not? If so, is there any test in the R program?</p>
<p>Thanks</p> | 71,489 |
<p>I am really stuck with this question:
The Mann-Whitney test requires homogenity of variance if a median difference is suppossed to be statistically significant.</p>
<p>In case homogenity of variance is not met, but the test is significant:
Which aspects of the test can I report? </p>
<p>Thanks a lot in advance. ... | 49,810 |
<p>I am trying to interpret the results of some experiments I have run, involving showing participants videos of animated synthesised speech.</p>
<p>I ran a mean opinion score test. I made 36 movies in total. 9 each with the following exaggeration factors: 1(A), 1.1(B), 1.2(C), 1.3(D). </p>
<p>11 participants were sh... | 71,490 |
<p>To validate the acoustic performance of a product, we are using hand-engineered features and thresholds. Everytime a new hardware problem arises we have to at least tweak a parameter and at worst add a new feature with its own parameters.</p>
<p>We now have tens of thousands of records, with some labeled, and I'm t... | 71,491 |
<p>Suppose I have $X_1 \sim N(\mu_1,\sigma^2_1)$ and $X_2 \sim N(\mu_2,\sigma^2_2)$ (where the distribution is empirically estimated). I believe that $X_1$ and $X_2$ are actually drawn from the same distribution $N_(\mu^*, \sigma^{*2})$. I think the MLE is just to say $\mu^*=\frac{\mu_1+\mu_2}{2}$ and similarly for var... | 32,982 |
<p>I wrote a simulation of a geometric Brownian motion which works like this:</p>
<ol>
<li>${ t }_{ i }-{ t }_{ i-1 } \sim Exp(\lambda )$</li>
<li>${ Z }_{ i }\sim N(0,1)$</li>
<li>${ Y }_{ i }\sim { e }^{ \sigma \sqrt { { t }_{ i }-{ t }_{ i-1 } } { Z }_{ i }+\left( \mu -\frac { { \sigma }^{ 2 } }{ 2 } \right) \lef... | 176 |
<p>We have 1 pre-stress measurement point (t1), then a severe stressor, and after many months, 3 consecutive measurement points (t2 t3 t4) that are very close together. We cannot really handle these as individual measurement points (they are very similar) - to increase reliability of these 3 timepoints t2-t4, we would ... | 71,492 |
<p>I'm analyzing reaction time data from a repeated measures ANOVA with the following design:<br>
Factor 1 (between-group): <code>GROUP</code> (controls, clinical)<br>
Factor 2 (within-group): <code>TASK TYPE</code> (social, non-social)<br>
Factor 3 (within-group): <code>DECISION DIFFICULTY</code> (easy, hard)</p>
<p>... | 1,668 |
<p>I have a large sequence of DNA in which every position can have 4 different states, or nucleotides (A,T, G or C). The distribution of the nucleotides in the sequence is non-random and, most importantly, different portions of the sequence (defined according to biological reasons) have different nucleotide distributio... | 921 |
<p>I have a dataset with 17 variables (one numerical, 16 categorical). The numerical variable is the execution time of a process. I'm using one of the categorical variables (100 levels) to predict the execution time. Box plots are given here in terms of execution time and those 100 levels: </p>
<p><img src="http://i.s... | 32,986 |
<p><img src="http://i.stack.imgur.com/9pa7S.jpg" alt="enter image description here"></p>
<p>I have a correlation matrix of 8,854 * 8,854 size. These are Pearson correlation coefficient values in the matrix. I want to perform Hierarchical clustering and create good resolution images like I have attached. A step by step... | 71,493 |
<p>I am looking for a resource where i can find derivation of the linear combination of multivariate t distribution. Does anyone here know any good site or place (s)he can point me to? I am trying to see if the linear combination of multivariate t distribution will give a multivariate t distribution. In other words, wh... | 71,494 |
<p>Two-sample comparison of proportions, sample size estimation: <strong>R vs Stata</strong></p>
<p>I got different results for sample sizes, as follows:</p>
<p>In <strong>R</strong></p>
<pre><code>power.prop.test(p1 = 0.70, p2 = 0.85, power = 0.90, sig.level = 0.05)
</code></pre>
<p>Result: $n = 160.7777$ (so 161)... | 10,756 |
<p>I've been reading Hoekstra et al's 2014 paper on "Robust misinterpretation of confidence intervals", which I downloaded from <a href="http://www.ejwagenmakers.com/inpress/HoekstraEtAlPBR.pdf">Wagenmakers's website</a>.</p>
<p>On the penultimate page the following image appears.</p>
<p><img src="http://i.stack.imgu... | 71,495 |
<p>it's embarrassing that I'm asking this but I always seem to forget the correct treatment of this subject:</p>
<p>So say the question is stated as follows:</p>
<p>What is the probability of drawing 4 aces from a standard deck of 52 cards.</p>
<p>is it:
1/52 * 1/51 * 1/50 * 1/49 * 4!</p>
<p>or do I simply say w... | 71,496 |
<p>Imagine that you are planning a study about risk behaviours among HIV positive injecting drug users.</p>
<p>All the individuals included in the sample are injecting drugs and all are HIV positive. The main “exposure” in the study is the person’s awareness about their HIV serostatus (some of the drug users do know t... | 71,497 |
<p>I am taking the time to learn how to analyze networks and want to test if there are differences between two networks over time. Since I am new to R and networks in general, I am hoping to get some help how to compare and analyze network graphs.</p>
<p>Simply, my dataset will contain information on flows between tw... | 71,498 |
<p>I came across an example where standard deviation was being plotted on a Cartesian plot (standard 2D with X and Y axes.)</p>
<p>This seems like a valid thing to do but in this case the example only had a single line running across the graph to "indicate" standard deviation. This to me seems not very useful, possibl... | 71,499 |
<p>I am not a traditional statistics guy. I am from an electrical engineering background. So, spare me for lack of jargon.</p>
<p>The model is to be used for predicting agricultural output based on previous data. One method is Grey model prediction, which need around 4 to 8 sample data for prediction. Could you think ... | 32,998 |
<p>I have a dataset on a particular domain and I want to do a one-class classification with LIBSVM (wrapper) in Weka. I have trained the classifier, but the problem is, when I test it with a different dataset than the test set, I get all of them as correctly classified (which I know they are topically different from th... | 71,500 |
<p>What are the main differences between the two-sample Kolmogorov–Smirnov test and the Brunner-Munzel test with respect to assumptions, power, etc? Both are non-parametric, and should work in the heteroscedastic case?</p> | 71,501 |
<p>Sometimes I want to do an exact test by examining all possible combinations of the data to build an empirical distribution against which I can test my observed differences between means. To find the possible combinations I'd typically use the combn function. The choose function can show me how many possible combin... | 33,000 |
<p>I have a linear model with 6 IVs and would like to analyze the effect of an interaction term applied to all the IVs.</p>
<p>To illustrate, let's say we're predicting the Win/Loose ratio of NBA basketball teams based on a number of players statistics and we want to add the number of spectators coming to the games as... | 33,001 |
<p>I have read <a href="http://stats.stackexchange.com/questions/6563/80-of-missing-data-in-a-single-variable">80% of missing data in a single variable</a> and understand the approach for dealing with missing data which simply cannot exist for 1 variable. </p>
<p>I am trying to generalise this up to 2 or more variable... | 71,502 |
<p>Suppose we have 500 students nested in 20 classes (different classrooms), 25 students per class</p>
<pre><code>student<-factor(1:500)
class<-rep(LETTERS[1:20],each=25)
</code></pre>
<p>They all take a test.</p>
<pre><code>score<-rnorm(500,mean=80,sd=5)
</code></pre>
<p>The model below would tell you abo... | 71,503 |
<p>Take the task of fitting an a priori distribution like the ex-Gaussian
to a collection of observed human response times (RT). One method is to compute the sum log likelihood of each observed RT given a set of candidate ex-Gaussian parameters, then try to find the set of parameters that maximizes this sum log likelih... | 71,504 |
<p><strong>Spectral Decomposition</strong></p>
<p>Let $\mathbf{A}$ be a $k\times k$ positive definite matrix with the spectral decomposition $\mathbf{A}=\sum_{i=1}^{k}\lambda_{i}\mathbf{e}_{i}\mathbf{e}_{i}^{\prime}$.
Let the normalized eigenvectors be the columns of another matrix $\mathbf{P}=\begin{bmatrix}\mathbf{e... | 43,913 |
<p>If I have 30 objects and 5 buckets that each hold 6 objects, how many times could I put the objects into the buckets without an object being in the bucket with an object it has previously been grouped with? So, for each round you would empty all of the objects from the buckets and place them into buckets again (they... | 71,505 |
<p>I am having difficulties to select the right way to visualize data. Let's say we have <strong>bookstores</strong> that sells <strong>books</strong>, and every book has at least one <strong>category</strong>.</p>
<p>For a bookstore, if we count all the categories of books, we acquire a histogram that shows the numbe... | 10,851 |
<p>I have a sequence of integers that represent total sales of my product for each day. From time to time, we have large press or marketing events that increase sales on the day of the event and for a few days after that but then eventually taper down to the long-run average. Here's some made-up numbers showing what I ... | 71,506 |
<p>I would like to test that two difference/distance/dissimilarity matrices are not the same. i.e. the rows and columns between the two matrices represent the same features, but the distances are obtained from 2 populations and I'm interested in whether the difference matrices "look different" between the populations.<... | 71,507 |
<p>I have a dataset in which I have measured a dependent variable (let's call it $Y$) along with several independent variables $(X_1, X_2, X_3)$. The independent variables are correlated with one another to some extent. I would like to understand how $Y$ varies with $X_2$ when $X_1$ and $X_3$ are held constant. What ap... | 33,009 |
<p>I sucessfully find the standard error of difference, but can't get the t value right.</p>
<p>According to <a href="http://www.graphpad.com/quickcalcs/ttest1/?Format=C" rel="nofollow">this calculator</a> , I am supposed to get a sd of 0.092, which I do.</p>
<p>But for some reason, when I do $t = \bar{d} / (sd / \sq... | 71,508 |
<p>Assume a multivariate dataset $\mathbf{x} = (x_1, ..., x_n)$ where $x_{i}$ are for example different sensors. Now, there are several techniques (e.g. Welch's method) to calculate the power spectrum of each of the sensors separately. Is there any method to calculate one "joint" power spectrum over all of the sensors?... | 11,951 |
<p>As I'm currently working on scan matching for outdoor environments I was wondering about the best metric to compare two occupancy octrees (one resulted from the scan matching and one ground truth reference octree). So far I came up with a few different approaches:</p>
<p>Ignoring the occupancy values:</p>
<p>•
Cal... | 71,509 |
<p>I have modified the original question.</p>
<hr>
<p>Does <a href="http://en.wikipedia.org/wiki/Beta_distribution" rel="nofollow">beta distribution function</a> $$f(x,\alpha) = \frac{[x^a(1-x)^b]^\alpha}{B(a\alpha+1,b\alpha+1)}$$
where $B$ is the beta function, approach delta function $\delta(x-a)$ on $[0,1]$ as $\a... | 71,510 |
<p>I am taking a course in data mining. I am not sure how a non linear SVM when transformed to high dimensional space becomes a linear classification problem. It would be good if someone can provide me an intuition on this.</p> | 71,511 |
<h2>Scenario</h2>
<p>I am inspecting the <a href="https://archive.ics.uci.edu/ml/datasets/Soybean+%28Large%29" rel="nofollow">Soybean data set</a>, which has a quite a number of missing values for various categorical variables.</p>
<h2><strong>Plan</strong></h2>
<p>My plan is to eventually perform data imputation. H... | 71,512 |
<p>I am working on analyzing volumetric information extracted from the brain. In particular we would like to compare the strength of effects across three different regions (say x, y, and z). However, the three regions grossly differ in size (say y is 10 times larger than x, and z is 20 times larger than x). We would li... | 71,513 |
<p>I understand that imbalance or skew in the target variable within your training data can negatively impact effectiveness. Does the same apply to the predictor/independent variables?</p>
<pre><code>y ~ B0 + B1*x1 + B2*x2
</code></pre>
<p>Consider this simple example. I am trying to predict <code>y</code>, a categ... | 71,514 |
<p>Let $CDF$ be the cumulative distribution function for the standard normal distribution. Let $Z$ be a standard normal random variable.</p>
<p>Then $CDF(Z)$ is uniformly distributed on the unit interval, so by integration we can show that $E(ln(CDF(Z))) = -1$.</p>
<p>My question: <strong>there an easy way to compute... | 71,515 |
<p>I am running experiments on cells which are given two different treatments. Treatment one is a control virus, and treatment two is an active virus. Due to the variability between cell lines, I always have to normalize the result from treatment two to that of the control treatment one. I then use a t-test to determin... | 71,516 |
<p>I have a dataset that is unbalanced, where I have a response variable (<code>age</code>) and 2 factors (factor 1 = <code>gender</code>; 2 levels = m and f; factor 2 = <code>kill type</code>; 3 levels = a, b, c). Sample sizes for each vary greatly depending on the <code>kill type</code>. I intend to examine how <code... | 33,013 |
<p>I'm trying to find the expected value of a random variable $t_i$ which is the solution of </p>
<p>$$\epsilon_i=\mu(t_i-t_{i-1})-\sum^{i-1}_{k=1}\frac{\alpha}{\beta}\left(1-e^{-\beta(t_i-t_k)}\right)$$ </p>
<p>where $t_1,..., t_{i-1} , \alpha, \beta, \mu$ are all known constants and where $\epsilon_i$ is a random v... | 71,517 |
<p>I'm having some trouble with this equation from the least squares model.</p>
<p>$$E[\parallel \mathcal {\hat {B}} \parallel ^2] = [E\parallel \mathcal {\hat {B}} \parallel] ^2 + trace ( \text {cov} [\mathcal {\hat {B}}])$$</p>
<p>$$ =\parallel \mathcal {\hat {B}} \parallel ^2 + \sigma_{e}^2 trace((X^{T}X)... | 71,518 |
<p><strong>Code:</strong></p>
<pre><code>library(caret)
#adaptative control resampling method for fitting svr
ctrlada <- trainControl(method = "adaptive_cv", number = 10, returnResamp = "final",
adaptive = list(min = 5,
alpha = 0.05,
... | 71,519 |
<p>I am trying to fit a curve to a histogram that looks roughly like exponential decay. <img src="http://i.stack.imgur.com/jT7UI.png" alt="histogram"></p>
<p>Since this is roughly similar to exponential decay, I figured a good model was</p>
<pre><code>counts ~ counts[1] * exp(-a * mids)
</code></pre>
<p>Which is cal... | 33,015 |
<p>I'm trying to make sense of some data and get statistical results on them.</p>
<p>What I have is the following: </p>
<pre><code>Subject TimeOfDay Test1 Test2 Test3
A 10:00 valA1 valA2 valA3
B 10:00 valB1 valB2 valB3
C 15:00 valC1 valC2 v... | 71,520 |
<p>I am a land surveyor working on specifications for GPS control networks, and have some questions this forum may help me solve.<br>
We typically measure many lines between points which are converted to 3D vectors, then thrown into a least squares adjustment program. Some of these points are held as "fixed" meaning t... | 33,019 |
<p>In multilevel models, it is possible to predict (not estimate) the random effects by Empirical Bayes after the model parameters have been estimated.</p>
<p>I know how to use the <code>ranef()</code> command to do that. However, I am interested in understanding the procedure. </p>
<p>Can someone provide an explanat... | 71,521 |
<p>I would love to perform a TukeyHSD post-hoc test after my two-way Anova with R, obtaining a table containing the sorted pairs grouped by significant difference. (Sorry about the wording, I'm still new with statistics.)</p>
<p>I would like to have something like this:</p>
<p><img src="http://i.stack.imgur.com/2RhiS... | 71,522 |
<p>In the thread
<a href="http://stats.stackexchange.com/questions/28247/confidence-interval-for-eta2?rq=1">Confidence Interval for $\eta^2$</a> it was proposed that if only limited statistics are available (in my case, <em>F, df1, df2</em>, means), one could calculate the 95% CI for $\eta^2$ by: </p>
<ul>
<li>transfo... | 71,523 |
<p>I’m reading a research paper and the author prepared two print-advertisements of jam, one with an old lady (Ad1) the other one with an exotic lady (Ad2). Both print-advertisements (Testanzeige) have the same written information.</p>
<p>Hypothesis: With the increase of the need for variation (CSI), the Advertiseme... | 33,023 |
<p>It was my understanding that MLE estimates were asymptotically unbiased. The following simulation therefore confuses me. Can anyone help me with my understanding here?</p>
<p>I estimate the parameters of 50 random Weibulls that I've simulated with shape = scale = 1 (using the Wikipedia/R parameterisation)</p>
<p>A... | 71,524 |
<p>First I have to apologize for any uncorrect naming or categorisation of my question, as I am an electrical engineer rather than a mathematican.</p>
<p>I have a simulation that outputs for a given number of input parameters one output value. As the simulation is pretty complicated, I don't know the statistical conne... | 43,952 |
<p>I am using the Metropolis-Hastings algorithm for phylogenetic inference. To do so I would like to draw the substitution matrix Q from the <a href="http://en.wikipedia.org/wiki/Models_of_DNA_evolution#GTR%3a_Generalised_time-reversible_.28Tavar.C3.A9_1986.29_.5B9.5D" rel="nofollow" title="Wiki">generalized time-rever... | 51 |
<p>I have an repeated measure (4 total measures) variable of severity, but two measures are high severity and two measures are low severity. I want to test the difference between high and low severity. I was going to use a mixed model like this: DV= severity + auditor + severity*auditor. Where severity is a repeated... | 71,525 |
<p>I'm currently working on a project measuring willingness to pay (WTP) for a particular product. The data we are collecting are continuous variables denominated in the local currency. One thing we are interested in is the "demand curve" for this product, expressed as the fraction of respondents willing to pay a par... | 33,027 |
<p>Note that for a homogeneous point process the density is just a number, while for an in-homogeneous process it is a function. In addition, how can I distribute that function on a larger study region than the initial points?<br>
<strong><em>Update 1:</em></strong><br>
<img src="http://i.stack.imgur.com/XS6Vz.png" alt... | 71,526 |
<p>I'm trying to fit a multilevel model for a repeated mesures design with three levels:
Sujects - conditions - trials. Each subject pass the test in two conditions, and there are 21 trials in each condition. Each trial is expected to be correlated in some manner with previous and following trial. </p>
<p>My problem i... | 43,962 |
<p>I'm working on implementing <a href="http://books.nips.cc/papers/files/nips24/NIPS2011_1271.pdf" rel="nofollow">streaming k-means</a> in <a href="http://mahout.apache.org/" rel="nofollow">Mahout</a>. The <a href="https://github.com/dfilimon/mahout/tree/skm/core/src/main/java/org/apache/mahout/clustering/streaming" r... | 134 |
<p>I have a data set of millions of directed line segments. The line segments are sequential (it's a time series over two climatic variables). If I plot them, I just get a blurred mess that's impossible to interpret, like this:</p>
<p><img src="http://i.stack.imgur.com/FTQAD.png" alt="lines"></p>
<p>(this is a subset... | 36,679 |
<p>In this <a href="http://www.jseepub.com/EN/article/downloadArticleFile.do?attachType=PDF&id=9027" rel="nofollow">paper</a> on particle filtering with gradient descent, the authors sample <em>X</em><sub><em>k</em>+1</sub> through gradient descent, then update the covariance matrix P associated with <em>X</em><sub... | 71,527 |
<p>Suppose $X_1, . . . , X_n$ are i.i.d. with pdf $f(·)$.<br>
We want to test the hypotheses
\begin{align}
H_0 &: f(x) = 2x , \;\, \text{ for } 0 \le x \le 1, \text{ against}, \\
H_1 &: f(x) = 3x^2 , \text{ for } 0\le x \le 1.
\end{align}</p>
<p>Show that the level-$\alpha$ likelihood ratio test is of the form... | 71,528 |
<p>I am getting the impression that when people are referring to a 'deep belief' network that this is basically a neural network but very large. Is this correct or does a deep belief network also imply that the algorithm itself is different (ie, no feed forward neural net but perhaps something with feedback loops)? </p... | 45,656 |
<p>I'm currently working on an Econometrics project and I've come to a point where I've dropped a high leverage point as identified by cook's distance and a leverage plot (had observations that were <em>twelve</em> standard deviations away from mean and a nonsensical entry). My regression model before I dropped the hig... | 43,963 |
<p>Akaike Information Criterion (AIC) and the c-statistic (area under ROC curve) are two measures of model fit for logistic regression. I am having trouble explaining what is going on when the results of the two measures are not consistent. I guess they are measuring slightly different aspects of model fit, but what ar... | 33,035 |
<p>First please note that this question is NOT a duplicate of <a href="http://stats.stackexchange.com/questions/33/r-packages-for-seasonality-analysis">R packages for seasonality analysis</a>.</p>
<p>What is the best way to remove seasonality on a edge? The usual methods have all huge edge effects. It there any recomm... | 33,036 |
<p>I have been using several techniques, sometimes in conjunction with one another, in a pre-processing pipeline prior to using the data for supervised machine learning.</p>
<p>I was wondering about the effects of the order that I perform the operations.</p>
<p>Several operations that I have been performing are:</p>
... | 33,037 |
<p>I asked this question on the Mathematics stack exchange site but I didn't get a response. If posting it here means it should be closed or migrated from there, is there a way that i can do that? Or can a moderator to it?</p>
<hr>
<p>In many queuing models it is assumed that the service time follows an exponential d... | 71,529 |
<p>Suppose I want to determine if treatment T affects parameter X, and by how much. I have a sample of subjects that received no treatment, and can calculate mean X(control) with associated variability. This allows me to estimate the true population mean of untreated population. The same goes for the treated population... | 71,530 |
<p>I need to learn both the VB and EM methods for Bayesian Networks. Before going into detail of both algorithms, which I am a bit aware of, I need to EXACTLY understand the basic motivations behind them. Different resources use the terms "inference, parameters, estimation, learning" so intermingled that I easily lose ... | 71,531 |
<p>I am looking for a way to have experts elicit a prior for a Normal-Inverse-Gamma Bayesian linear regression model. Is there any material suggesting intuitive ways to go about this?</p> | 71,532 |
<p>I have a time series (let's say $X_1$ to $X_n$), and I need to predict the next sample (let say $X_{n+1}, X_{n+2},\dots, X_{n+k}$) using model such as neural network, or multiple linear regression. At time n, I have all the sample from $X_1$ to $X_n$, and need to predict $X_{n+1}$; at time $n+1$, I have all the samp... | 43,972 |
<p>I'm trying to sort out two different uses of the term "compound distribution" and figure out the relationship.</p>
<p>The Wikipedia article on <a href="http://en.wikipedia.org/wiki/Compound_distribution" rel="nofollow">compound distribution</a> -- which I wrote -- defines a compound distribution as an infinite mixt... | 43,975 |
<p>Is it ok to use the Spearman's rho if one has to correlate a binary and a discrete (from 0 to 100) variable? Or Kendall's tau b would be a better choice?</p> | 33,047 |
<p>Is there any way to investigate minor contributing $X$ variables in a model when there are one or two $X$ variables which contribute to the explanation of a majority of the variation in the $Y$ variable?</p>
<p>If I simply remove these, I get overfit, whereby the software tries to overemphasize the remaining variab... | 71,533 |
<p>My data has normally distributed dependent variables; however the independent variables are an eclectic mix.
They include categorical, nominal, continuous normal, continuous non-normal, and almost bimodal.</p>
<p>Which methods would be most appropriate for this? I can use both linear and nonlinear methods, includin... | 71,534 |
<p>In a data analysis, does it make sense to report both Kendall's tau and Goodman's Gamma? I guess not, since tau looks like a standardized form of Gamma. Or does it add some explanation?</p> | 33,048 |
<p>I am using <code>earth package</code><a href="http://cran.r-project.org/web/packages/earth/index.html" rel="nofollow">earth: Multivariate Adaptive Regression Spline Models</a> regression to get a constant piecewise approximation of my data. I want to plot a band of confidence around it. Does this make sense to esti... | 33,049 |
<p>I have a large list of time series data which is derived from sensors from a machine. It includes e.g. name of machine, temperature of part 1, temperature of part 2, velocities etc.
I also have another dataset which contains all repairs for this machine (and which component this repair was on). My goal is to predict... | 33,051 |
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