question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I am working on a text classification problem. My data is highly imbalanced. For example, one category has 700 documents while the other has 30. I have around 30 categories. I tried different classifiers and the performance is consistently poor.</p>
<p>What is the best way to tackle this issue? Thanks</p> | 37,667 |
<p>I was told the following will generate 52 observations in range (1,52), with a shape parameter of .5 and a scale parameter of 2. </p>
<p>Yet, there is a 67 so that is perhaps wrong?<br>
What I need is N observations in range (1,52) with the observations conforming to a Weibull distribution with specific parameters... | 32,545 |
<p>I'm designing large-scale, regularized logistic regression models with lots of sparse, binarized features. e.g. isUS, isFR, etc. As a result, a lot of the weights in the model are zero.</p>
<p>I'm wondering how I should compute the "number of parameters" in model-selection criteria like AIC, BIC, etc. Should I only... | 71,194 |
<p>I am running anchored analyses in Winsteps on four data sets (a full data set as well as the data degraded by an additional 20%, 50%, and 70%). I noticed that the standard errors are labeled ERROR for the full data and the data that is degraded an additional 50%, but are labeled MODLSE for the data that is degraded ... | 71,195 |
<p>I suspect this question is related to:
<a href="http://stats.stackexchange.com/questions/78596/when-combining-p-values-why-not-just-averaging">When combining p values, why not just averaging?</a></p>
<p>Let me explain my problem: </p>
<ul>
<li><p>Suppose you have a set of sample means and associated p-values, stan... | 32,548 |
<p>I have some logged increments from time series data and wanted to fit a lognormal distribution, but obviously some are negative. How can I do this?</p> | 32,550 |
<p>I am looking for a comparison of different regression tree node splitting approaches within the random forest framework. I am looking at the trade-off between ensemble accuracy/reliability (holding forest size constant) and computational complexity of the split since I deal with large datasets. </p>
<p>The standard... | 71,196 |
<p>I have performed a log transformation on my skewed data, however on my DV it went from positive skew to negative skew after the (log) transformation, further data was missing from my DV after the transformation. Please help</p> | 71,197 |
<p>I already asked a first question <a href="http://stats.stackexchange.com/questions/17006/interpretation-of-incidence-rate-ratios">here</a> fortunately or unfortunately the answers support my understanding of the general problem. Too bad this doesn't solve the problem.</p>
<p>So, here is the thing:
I am fitting a ra... | 71,198 |
<p>I was reading this paper <a href="http://stat.duke.edu/phd-program/gcc/resources/ResourcesDocuments/CodeExplanation.pdf" rel="nofollow">http://stat.duke.edu/phd-program/gcc/resources/ResourcesDocuments/CodeExplanation.pdf</a> related to Gibbs sampling.</p>
<p>Suppose we have n iid samples $x_i$ from $N(\mu,\sigma^2... | 71,199 |
<p>In an article by Hofmann <a href="http://cs.brown.edu/~th/papers/Hofmann-UAI99.pdf" rel="nofollow">pdf</a>, he proposes: </p>
<blockquote>
<p>initialize $β$ to one, run until convergence, then rescale $β$ by a
factor $η<1$, run again until convergence, and iterate this until
changing $β$ no longer improves... | 71,200 |
<p>I have a series of candidate spatial capture-recapture models--but 2 or 3 of these models end up generating data vectors that R can't allocate when considering the entire dataset. I've split observations into two groups, and fit each candidate model twice, and have been able to piece together estimates and variance... | 32,555 |
<p>Cardiologists have a tool called EUROScore used to adjust the risk associated with performing heart surgery. It comes into play when, for example, one surgeon is recognised as being more expert and so takes on the riskier patients: it adjusts his/her performance measures to take this into account. It also helps the ... | 71,201 |
<p>Suppose we want to bid on a piece of land when one other bidder is interested. The seller announced that the highest bid in excess of \$10,000 will be accepted. Assume that the competitor's bid $X$ is a random variable that is uniformly distributed between \$10,000 and \$15,000.</p>
<ol>
<li><p>Suppose you bid $12,... | 71,202 |
<p>I am new to statistical modelling and so please pardon if the question appears trivial. </p>
<p>I have a set of multi-dimensional data ($T$) where each dimension represents features ($f_i$) obtained from a mammogram. For example $T_1=(f_{11}, f_{21} f_{31},\ldots, f_{n1}); T_2= (f_{12}, f_{22}, f_{32},\ldots, f_{n2... | 71,203 |
<p>Data $(x_1, y_1), \dots, (x_n, y_n)$ is modelled with $x_i$ being non random and $y_i$ being observed values of $$Y_i = \alpha + \beta (x_i - \bar x) + \sigma \epsilon_i$$ with $\epsilon_i \sim N(0,1)$. </p>
<p>I have calculated the MLE's of the parameters $\alpha, \beta$ and $\sigma^2$ with $\hat \alpha = \bar y$ ... | 71,204 |
<p><strong>Scenario Construction:</strong></p>
<p>I have a MFCC generator block which gets the speech samples from the user and generates a rectangular matrix say $A$ of the order $m \times n$, whose elements are the Cesptral Coefficients(MFCC). Now, suppose I maintain a database which are previously stored containing... | 71,205 |
<p>I want to proof the "Relative Age Effect" of a football team. I have a list of birth dates of the team members (about 20 numbers between 1 and 365, the day of the year).
I now want to use the KS-Test to test against a uniform distribution.</p>
<p>this is how I did it, but it looks very wrong to me:</p>
<blockquot... | 43,387 |
<p>I am working on a machine learning project where I am trying to fit a curve on data. Unfortunately the date has somewhat high feature vector. So, I can't really plot them on a 2D or 3D space to guess how the shape of the data looks like. </p>
<p>So, other than hit and trial, does there exist a mathematical way to f... | 43,388 |
<p>I'm trying to prove that $\lim_{n\rightarrow\infty}F_{X}(n)=1/2$ when $X\sim \text{Poisson}(n)$ without success. Could someone help me ?</p> | 71,206 |
<p>I apologize for all those questions on modelling. It is the very first time that I try GLM and I am really lost even after reading a lot of papers.</p>
<p>I have divided my covariates according to their theme e.g. topographic variables together. I was trying to first get the most parsimonious model for each set of ... | 71,207 |
<p>I first summarize the analysis of some papers that I want to imitate. The regression looks like:</p>
<p><code>Y2(subjects) = Y2(friends) + Y1(subjects) + Y1(friends) + Z(subjects)</code></p>
<p>Where <code>subjects</code> refers to focal people and <code>friends</code> refers to those subjects connect to. Some one... | 71,208 |
<p>I have a large population of size $n$ from an unknown continuous random variable $X$, and I do not know the underlying distribution of $X$. Given a constant number $c$, I want to determine the minimum sample size I need to estimate the probability $P(X \le c)$ given a confidence level, $p_c$, and confidence interval... | 71,209 |
<p>So I have maybe an unusual question. I have some simulation data that I use as input into a theoretical model. The problem is that the simulated data is noisy and this causes divergences when I try to input it into my theory. Well I figured out what conditions my simulated data must satisfy to ensure that I don't... | 71,210 |
<p>How to do this? I use SVMlight that returns me some scores (which say how sure SVM is that something belongs to a class?)</p>
<p>The questions is - can I do something to convert it to a % probability? Any formula, method that I could code for myself? Or is this impossible?</p> | 71,211 |
<p>I'm a UI Designer/Developer working at a start-up with a LOT of data. I'm looking to do some training in Data Viz techniques. Anyone have suggestions for classes in NYC? Or online, if there are some good sites. </p> | 965 |
<p>Is there any relationship between $R^2$ and sample size - does the $R^2$ increase with sample size? And does the adjusted $R^2$?</p> | 8,316 |
<p>I know that the mathematically, p values should be uniformly distributed under the null hypothesis. However, what is this null hypothesis (in this context)? </p>
<p>Can someone give me an example please ? </p> | 49,527 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/13550/prcomp-vs-lm-results-in-r">prcomp() vs lm() results in R</a> </p>
</blockquote>
<p>I have 4 vectors that are 4 historical stocks prices. This is my R code:</p>
<pre><code>> x <- c(1,2,3,4,5,6)... | 49,867 |
<p>I have recently come across the mircosoft data analysis tool add-on, and I was wondering if there was something comparable that can be used with OpenOffice? </p>
<p>However, if there is nothing for OpenOffice, is there any other software that can be used in Ubuntu-Linux that can do similar things?</p> | 71,212 |
<p>I have a data-set consisting of N p-dimensional observations (all quantitative variables). I want to apply a hierarchical clustering algorithm to those data. As explained on page 505 in <a href="http://www-stat.stanford.edu/~tibs/ElemStatLearn/" rel="nofollow">Elements of Statistical Learning</a>, when using weighte... | 71,213 |
<p>I am looking for a one-dimensional distribution that can be fit to bus-delays. The data are real numbers (positive and negative), and exhibit both skewness and kurtosis.</p>
<p>Which distribution should I use to fit these data?</p>
<p>I would like to compute MAP or ML estimates, and I am using Matlab.</p> | 71,214 |
<p>I have the following table and I would like to make a representative chart.</p>
<pre><code> Start End Duration
Implementation of project 01/05/2012 30/04/2014 24
XRD and Polymerisation 01/05/2012 01/06/2012 1
DFT 01/05/2012 01/11/2012 6
Supervision... | 32,568 |
<p>I'm using this python script for Holt-Winters forecasting (<a href="https://gist.github.com/andrequeiroz/5888967" rel="nofollow">https://gist.github.com/andrequeiroz/5888967</a>) that I believe chooses values of alpha, gamma and beta via RMSE optimisation.</p>
<p>Sometimes the output gives strange values, 1.0 and 0... | 71,215 |
<p>I have problems finding a solution regarding how to run a post-hoc test (Tukey HSD) after a 2-factor (both within-subjects) repeated-measures ANOVA in R. For the ANOVA, I've used the aov -function: </p>
<pre><code>summary(aov(dv ~ x1 * x2 + Error(subject/(x1*x2)), data=df1))
</code></pre>
<p>After reading answers ... | 43,409 |
<p><strong>Context</strong>: Latent Growth Curve Modeling for continuous variable with 15 time points. One <code>intercept</code>, two <code>slopes</code> (for first and second half of all time points). N=146, >90% data coverage, <code>MLR</code> estimator in MPlus, no covariates.</p>
<p><strong>Problem</strong>: Hig... | 71,216 |
<p>I am trying to understand the poem <a href="http://www.columbia.edu/~to166/hiawatha.html" rel="nofollow">Hiawatha Designs an Experiment</a> because it looks like the kind of in-joke that it would be nice to get, as a statistician. Here is what I would like to know:</p>
<p><strong>Unhelpful answer:</strong>
"The poe... | 71,217 |
<p>I've been researching the <a href="http://cran.r-project.org/web/packages/mice/index.html">mice</a> package, and I haven't yet discovered a way to use the multiple imputations to make a Cox model, then validate that model with the <a href="http://cran.r-project.org/web/packages/rms/index.html">rms</a> package's <cod... | 71,218 |
<p>What are some examples of NP-hard optimisation problem that requires approximate methods (such as Monte Carlo? I have done a lot of research but I can't find a suitable problem to implement apart from the Travelling Salesman Problem</p> | 71,219 |
<p>I'm trying to graph the number of actions by users (in this case, "likes") over time.</p>
<p>So I have "Number of actions" as my y-axis, my x-axis is time (weeks), and each line represents one user.</p>
<p>My problem is that I want to look at this data for a set of about 100 users. A line graph quickly becomes a j... | 71,220 |
<p>I have a binary classification problem which is very unbalanced - it can have 98% of data from one class. Which classifiers work well with this sort of data? </p>
<p>I have an unlimited supply of training data, since I produce it using a pseudo random number generator. However, I found that to get a neural netwo... | 71,221 |
<p>I am working with predictive models for wind speeds, which have been given as Gumbel distributions. I need to convert the wind speeds to wind pressures using the formula:</p>
<p>$Pressure = Density * Velocity^2$</p>
<p>So my question is how do I determine the distribution parameters for the wind pressure given the... | 32,577 |
<p>I am having trouble finding the technical term for a scale used in survey research with opposite values at both ends of the scale. For instance, how can I refer to a scale of the following kind:
In your opinion, who is responsible for health care?
Government (1) --- (2) --- (3) --- (4) --- (5) Citizens?</p> | 32,578 |
<p>I would like to ask if I have an event when flipping a coin for $n$ times until a <strong>first</strong> head is observed.</p>
<p>Event $E$: the first head on even numbered flip</p>
<p>Event $H$: head on first flip</p>
<p>Let $P(H) = p$</p>
<p>I am required to find $P(E)$</p>
<p>I know $P(E) = P(E|H)P(H) + P(... | 71,222 |
<p>I know that there are many related threads, packages and papers. Currently I`m reading through many of them. However, I don't plan to dig too deeply into this topic. I need a sound method that works with strongly dependent univariate time series (in large samples). My champion so far is the Kokoszka & Leipus tes... | 71,223 |
<p>Are there any other methods for an $m\times n$ contingency table with $m$ or $n$ greater than 2 for use with small samples ($np<5$) other than Fisher's exact test?</p> | 32,580 |
<p>I have a question regarding interpretation of regression results based on data where I have some negative values. Since the residuals were positively skewed I needed to log-transform my data, and because of negative values my log transformation looked like $\ln(Y-\min(Y)+1)$. Normally, if we have $\ln$ in both sides... | 49,479 |
<p>I was wondering if there is a minimum sample size for conducting discrete choice experiment. From what I know, if choosing the number of sample size is a problem, one can resort to using the magic number of 400+. Although it would be nice to have such sample size, but then this kind of experiment is expensive, so 40... | 71,224 |
<p>I am working on a housing problem in which I use dichotomous and ratio data to predict
housing production (units constructed in a year-ratio) in a 17 year time period. At this time, I am using OLS and as I get better at stats, I shall attempt this problem using time-series analysis. That said, I have used R to stan... | 71,225 |
<p>I have developed a simple <em>Kernel Density Estimator</em> in Java, based on a few dozen points (maybe up to one hundred or so) and a Gaussian kernel function. The implementation gives me the PDF and CDF of my probability distribution at any point.</p>
<p>I would now like to implement a simple <em>sampling method<... | 71,226 |
<p>I am doing a cross-validation study, training a model on an input to predict a target.</p>
<p>During training, my model generates an output vector that is guaranteed to be the same size as the corresponding training target vector. I can use metrics such as $R^2$ or RMS error to quantify this.</p>
<p>During testing... | 43,421 |
<p>Recovering values from an estimated Pareto distribution</p>
<p>A couple of weeks ago I asked a question about the Pareto distribution, wanting to understand how the units of measurement are related in order to make the usual statements about the invariance of the relationship between the percentage of people and t... | 71,227 |
<p>I have heard about q-values, in lines of p-values. What is the main benefit of using q-values over p-values? Why is it that p-values have to be adjusted?</p>
<p>Wikipedia only has two lines of mention as follows: "The q-value is defined to be the FDR analogue of the p-value. The q-value of an individual hypothesis ... | 71,228 |
<p>I am hydrologist and I am looking for a solution for the following problem:</p>
<p>Suppose that I have $k$ regions each yielding a sample of the same variable (e.g., annual peak flow) drawn from different sites within the given region (each sample $i=1,..K$ has a record length $n_i$).</p>
<p>The homogeneity test ... | 32,586 |
<p>I am attempting to compare a two pitching stats (W/L% and ERA) to determine to what extent the latter can predict the former. After entering my data and performing the appropriate linear regression analysis I am left with two seemingly contradictory results.
1) I have an R-sq value of .257 which would lead me to sta... | 71,229 |
<p>If f is a pdf, the integral of x*f(x) over the entire range where f(x) > 0 gives, of course, the expected value. Suppose that integrate the same function, x*f(x) from negative infinity up to t, giving a new function, G(t). So G(t) = E(x | x < t), and is measured in the same units as x, as the expected value is ... | 71,230 |
<p><strong>[Edit]</strong></p>
<p>In light of the feedback I have received, I have added some more information below, to help clarify what I am seeking to 'model'.</p>
<p>Additionally, I have reformualted the problem from a "dog barking warning system" to something else which hopefully, has less ambiguity. Instead, I... | 71,231 |
<p>I have found the term "asymptotic power of a statistical test" only related to the Kolmogorov-Smirnov test (to be precise: asyptotic power = 1). What does this term acctually mean? In my opinion it should be someting like this: "if the alternative hypothesis is true, than for every significance level alpha there exi... | 50 |
<p>I am comparing two group means on two dependent variables (aggression and stress levels) using Mann-Whitney U test by SPSS. My question is that do I need to adjust the alpha level for this? </p> | 71,232 |
<p>Suppose I have a set of observations on a finite (continuously divisible) quantity $Q$ (say $Q = 100$ to be concrete). For each observation $i$, $Q$ is partitioned into three parts $(A_i, B_i, C_i)$, so my observations look like</p>
<p>$(10,50,40)$<br>
$(33,34,33)$<br>
etc</p>
<p>Now I want to test the hypothesis ... | 71,233 |
<p>I have a bunch of user ratings, over time, for different products, and I'd like to figure out the best ways to analyse and compare them. </p>
<p>Here's how the data looks: </p>
<pre><code>Product, Week, 1 star, 2 star, 3 star, 4 star, 5 star
Product A, Week 1, 2, 0, 0, 10
Product A, Week 2, 3, 1, 1, 9
Product B, W... | 71,234 |
<p>On his blog, Larry Wasserman has a <a href="http://normaldeviate.wordpress.com/2012/08/13/what-to-teach/">post</a> about what he planned to cover in his course last fall. He notes that he was abandoning some classical topics in favor of more modern issues. One topic that he mentions is Hoeffding’s inequality. What m... | 32,592 |
<p>I have a large dataset that has many variables. I'm trying to determine which variables correlate strongly with one specific variable. When you look at the entire dataset as a whole, the correlation of different variables is pretty weak.</p>
<p>I know, however, that within certain subsets of the data the correlat... | 71,235 |
<p>What is the limit for Hausman test? </p>
<pre><code> hausman onefe one
---- Coefficients ----
| (b) (B) (b-B) sqrt(diag(V_b-V_B))
| onefe one Difference S.E.
-------------+------------------------------------------... | 71,236 |
<p>Consider sampling data from a population of size $N$ in the following way: For $k=1, ..., N$ </p>
<ol>
<li><p>Observe individual $k$'s "disease" status</p></li>
<li><p>If they have the disease, include them in the sample with probability $p_{k1}$ </p></li>
<li><p>If they do not have the disease, include them with p... | 32,595 |
<p>Two random number generators with uniform distributions having min, max as (0,8)
The first generates all integers between 0 and 8 uniformly.
But the second generates only [0,2,4,6,8] uniformly.</p>
<p>What is the difference between the second generator and the first? Smaller range, but scaled up? A discrete vs. con... | 71,237 |
<p>I want to compare the relative variability of several sleep-related variables in the same group of subjects. For example, is there more variability in time spent in REM sleep compared to the number of eye movement in REM sleep? These variables have different scales, which does not allow me to simply compare their v... | 8,477 |
<p>According to the Wikipedia article on <a href="http://en.wikipedia.org/wiki/Unbiased_estimation_of_standard_deviation">unbiased estimation of standard deviation</a> the sample SD </p>
<p>$$s = \sqrt{\frac{1}{n-1} \sum_{i=1}^n (x_i - \overline{x})^2}$$</p>
<p>is a biased estimator of the SD of the population. It st... | 49,576 |
<p>I tried to compare the following two models using "anova.lm()" in R:</p>
<pre><code>Model 1: score ~ gpa + class
Model 2: score ~ gpa
Res.Df RSS Df Sum of Sq F Pr(>F)
1 90 213
2 91 201 1 96 14.07 <2.2e-16
</code></pre>
<p>Since t... | 8,478 |
<p>I have a set of data which contains answers to a questionnaire (questions about satisfaction rated 1 to 5) and some demographic information (sex, age). I can divide the data in two groups and I want to see if there is any statistical difference between those groups. I tried the Wilcoxon test, but I have many ties, s... | 49,868 |
<p>I have a very stupid doubt: consider the real valued random variables $X$ and $Z$ both defined on the probability space $(\Omega, \mathcal{F},\mathbb{P})$. </p>
<p>Let $Y:= g(X,Z)$, where $g(\cdot)$ is a real-valued function. Since $Y$ is a function of random variables it is a random variable. </p>
<p>Let $x:=X(\o... | 71,238 |
<p>Let's say $x$ is correlated to both $y_1$, and $y_2$. Why are the residuals of the nested regression of $x$ against $y_1$ and $y_2$, not equal to the residuals of the simultaneous (multiple) regression of $x$ against $y_1$ and $y_2$? To clarify:</p>
<p>I take the residuals of the regression of $x$ against $y_1$ to ... | 71,239 |
<p>I'm watching a video on the EM algorithm,</p>
<p><img src="http://i.stack.imgur.com/Z5mcu.png" alt="enter image description here"></p>
<p>When we use Bayes' Theorem to calculate $b_i$, how do I find $P(b)$ and $P(a)$ initially? It says we can estimate the priors $P(b)$ and $P(a)$ but that's once we have at least o... | 71,240 |
<p>I’d like to illustrate my problem with a little (heavily abbreviated) excercise. I think it will help a lot to stress my point.</p>
<p>Meet Mary, Tom
and Jane. They all are programmers. Mary is a decent programmer. In
writing five programs she usually makes about 3 mistakes. Tom on the other
hand is quite bad. He ... | 71,241 |
<p>Given $CH(k) = [B(k) / W(k) ] \times [(n-k)/(k-1)]$, where
$n$ = # data points
$k$ = # clusters
$W(k)$ = within cluster variation
$B(k)$ = between cluster variation.</p>
<p>It is my understanding that the CH index can show the optimal number of clusters when doing k-means or hierarchical clustering; you would choos... | 71,242 |
<p>Let $X \sim U(0,1)$ and let $0 < a < 1$, then find </p>
<p>i) $P(X \le x|X > a)$</p>
<p>ii) $P(X \le x|X < a)$</p>
<p>I have the answers, but I'm wondering if someone can explain the process to me. </p> | 71,243 |
<p>Anyone know of one? I was looking at SVM-light but it seems like you can only use it in the binary classification setting. There is also SVM-multiclass but that doesn't have tSVM support. Any help appreciated. Thanks!</p> | 71,244 |
<p>I am trying to fit an <a href="http://www.stata.com/manuals13/tsucm.pdf" rel="nofollow">unobserved components model</a> for revenue and transactions for a firm where I also use some exogenous variables that capture economic conditions. The UCM decomposes a time series into trend, seasonality, an idiosyncratic compon... | 32,604 |
<p>I need to estimate specific lag ARMA model. Here is an example.</p>
<pre><code>ts1 <- arima.sim(list(order = c(0, 0, 5), ma = c(0, 0.7, 0, 0, 0.1)), n = 1000)
</code></pre>
<p>The above model is $X_t = Z_t + 0.7 Z_{t-2} +0.1 Z_{t-5}$, where $\{ Z_t\}$ is white noise.</p>
<p>Is it possible to estimate this mode... | 71,245 |
<p>Given that we partition a Gaussian random vector $\textbf{x}$ into three groups, $\textbf{x}_a$, $\textbf{x}_b$, and $\textbf{x}_c$, with a corresponding partitioning of the mean vector $\mu$ and of the covariance matrix $\Sigma$ in the form</p>
<p>$\mu = \begin{pmatrix} \mu_a\\ \mu_b\\ \mu_c\\ \end{pmatrix}, \ensp... | 71,246 |
<p>I have been given this formula for upper tail dependence and read that tail dependence depends on the copula and not the marginals:
$$
\lambda_U = \lim_{a \to 1} \Pr[Y>F_Y^{-1}(a)\mid X>F_X^{-1}(a)] .
$$</p>
<p>Would the inverse functions $F_X^{-1}(a)$ and $F_Y^{-1}(a)$ be copula functions ? </p>
<p>I have a... | 32,607 |
<p>N.B. I only have a very basic statistics background since I am in grade 9 in high school. Any help would be GREATLY appreciated.</p>
<p>My Experiment:</p>
<p>-Part 1: 2 variables (A and B) were each sampled in my homemade wind tunnel simultaneously (1000/s) for 10 seconds=10,000 data points in a run (Run 1) for Co... | 32,608 |
<p>I am comparing measures of a DV x with two group factors (2-way ANOVA) - y (with 2 levels) and k (with 3 levels). Both present significant main effects (p<.001) and high partial eta squared (above 0.6). The interaction effect is also significant (p<0.001) but the partial eta squared is 0.029. Post-hoc testing ... | 71,247 |
<p>I was making an attempt to solve the following problem sets, however, my answer <strong>15.913</strong> seemed quite different from that in the answer key <strong>16.84</strong>. I have checked my answer a few times and re-doing the question as well, but I was consistently pulled back to the same outcome of <strong>... | 71,248 |
<p>I listen for tweets matching keywords. When I receive a tweet, it may or may not be part of the set of things I'm interested about. Think about the Gemini Awards, a show similar to the Oscars, in Canada. #Gemini also happens to be an astrological sign, and many, many, many people talk astrology on Twitter. Now, imag... | 32,611 |
<p>I have a large data set: over 100,000 data points, each with 60 dimensions. I want to display the data in 2D to visibly maximize the separation between classes, which I know for each point. I asked a <a href="http://stats.stackexchange.com/questions/16305/dimensionality-reduction-technique-to-maximize-separation-of-... | 71,249 |
<p>I have a meta analysis at hand. I have reported on the quality of the included studies in a narrative form. But after I was requested about "quality assessment". I guess it might be something else, a statistical model for example, something like weighting.</p>
<p>I googled it but to my surprise, no good links were ... | 71,250 |
<p>We ran a 3-way ANOVA getting a non-significant result, but in doing so we saw that one condition looked like it had a strong effect. We tried a Bonferroni-corrected t-test of just that group, and it turned out significant. Is it valid to consider this? Is there some other correction needed to deal with the fact t... | 71,251 |
<p>I have a campaign that had two interventions A and B that were run in 3 markets each. I, also, had a control in 15 markets where no interventions were run.</p>
<p>For the markets where intervention A was run we had 5 units sold in the time period before intervention and 5 units during intervention.</p>
<p>For the ... | 71,252 |
<p>I'm doing a two-way between-within ANOVA in SPSS. I have two groups with 9 subjects each (so total = 18), and 24 levels of one repeated measure.</p>
<p>I understand why Mauchly's test of Sphericity has no meaning when there are are only 2 levels of a repeated measures factor, but I notice (using General Linear Mode... | 71,253 |
<p>My question is as follows:</p>
<p>Ratio=Ratios + log (numbers) +dummy variables + volatility</p>
<p>I have this type of regression in a paper published by the Federal Reserve Bank.Can someone tell me why we took the log of variables that represent numbers (such as size,and fees) whereas for the fractions such as (... | 71,254 |
<p>I came across the term Factorization Machines in recommender systems. I know what Matrix Factorization is for recommender systems but never heard of Factorization Machines. So what's the difference?</p> | 71,255 |
<p>Can you please explain what the next GARCH results mean?
where in these results can i know how well does the model forecast?</p>
<p><img src="http://i.stack.imgur.com/lGFwf.jpg" alt="garch"></p> | 71,256 |
<p>I have a historical dataset of about 1500 events representing structure fires in the Bay Area over the last few years. I'm building a small dashboard that displays these events by month, and would like to build in a prediction that shows the number of events expected to occur for the rest of the month for compariso... | 71,257 |
<p>Forgive me, I am forgetting my basic statistics.</p> | 49,595 |
<p>I am reading <a href="http://www.genomics.princeton.edu/hopfield/PDFs/TSP.pdf" rel="nofollow">this paper</a> by Hopfield et al. On page six, the authors defined the energy function of the Traveling-Salesman-Problem (TSP) mapped onto an artificial neural network as follows:</p>
<p>$$E = \frac{A}{2} \sum_X \sum_i \su... | 71,258 |
<p>I'm kinda confused. Is there a difference between Deep belief networks and Deep Boltzmann Machines? Are they different stuff or same thing?!</p>
<p>If so, what's the difference?</p> | 71,259 |
<p>I've collected environmental data on the dust level using direct-reading instruments. The outputs from the instruments are concentrations recorded at each minute over 1 hour. The data collected at many locations and locations are grouped into Groups and Department. The data looks like this in wide format</p>
<pr... | 71,260 |
<p>Suppose that $ X_{0},X_{1},\ldots,X_{n} $ are i.i.d. random variables that follow the Poisson distribution with mean $ \lambda $. How can I prove that there is no unbiased estimator of the quantity $ \dfrac{1}{\lambda} $?</p> | 71,261 |
<p>all!</p>
<p>I have a bit theoretical question - imaging, you trained several classifiers of the same type on the several datasets, that are in some sense close to one another (for example, they have intersection, or the ranges of parameters, that are being estimated, are close to each other)</p>
<p>Does it make an... | 71,262 |
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