question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>If there are multiple possible approximations, I'm looking for the most basic one.</p> | g65266 | [
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<p>Is there an analytic method to compute the expected first hitting time of an IID jump process with exponentially distributed time steps and jump sizes given by a Poisson random variable multiplied by a random variable that takes values {1,-1} with probability 0.5?</p> | g23776 | [
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<p>My Linear Models professor said that it is possible sometimes to obtain two different linear models for the same data, such that the models cannot be compared to determine which is better. How can this be?</p>
<p>As an example he mentioned models that have different scales. What does it mean for models to have dif... | g65267 | [
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<p>We are using a mixed model to describe trends as subjects age. We have multiple measurements per subject of a continuous outcome. We also adjust for the age at entry into the study. It is of interest if early entry and long follow-up are associated with different outcomes than late entry and short follow-up (i.e.... | g65268 | [
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<p>I understand that there is a function in R called <code>poly()</code> that can generate orthogonal polynomials--useful for applying on input variables before running a predictive model.</p>
<p>My question is that what is the role of categorical variables when we generate polynomials? Are they to be excluded?</p>
<... | g65269 | [
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<p>I have a cell array containing the gender e.g.</p>
<pre><code>GENDER = {'Male';'Female';'Male';'Male';'Male';'Female';'Female';'Female';'Male';'Male'};
</code></pre>
<p>and another array containing the respective groups e.g.</p>
<pre><code>GROUPS = [1; 2; 1; 1; 3; 3; 1; 2; 2; 3];
</code></pre>
<p>I would like to... | g65270 | [
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<p>I'm trying to train a support vector machine on a set of training data (which is seperate to my testing data).</p>
<p><code>training_data</code> has size <code>MxN</code> where <code>M = 10175</code> and <code>N = 102</code></p>
<p>Each observation has a label <code>1</code> or <code>0</code>.
(118 observations ha... | g28313 | [
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<p>For regression with ordered response variable, there are different methods, for example, discriminant analysis, probit or logit model. I am wondering what are the different focuses of the different methods and which one is more often used.</p> | g23779 | [
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<p>I'm trying to analyze some data consisting of five randomized parameters and a utility function which indirectly depends on the parameters, by experimentation. That is to say, the parameters of the experiment are chosen randomly, and successes and failures are counted up. I want to find parameters for which the ex... | g23780 | [
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<p>Instead of logistic regression when there is a prospectively follow cohort experiencing events there are methods to estimate a relative risk = RR (rather than an odds ratio)
eg <a href="http://aje.oxfordjournals.org/content/159/7/702.full.pdf+html" rel="nofollow">http://aje.oxfordjournals.org/content/159/7/702.full.... | g65271 | [
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<p>I have an experiment where I throw a biased coin were with confidence interval [0.38, 0.42] and confidence level of 0.95 I will get heads. If I get heads then I throw a biased 6-sided die which gives me 1 with probability given in the interval [0.48, 0.52] and confidence level 0.90.</p>
<p>What is the probability o... | g65272 | [
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<p>So I have collected data for 50 years of my dependent variable (continuous) data (x), independent (continuous) variable (y) across 10 locations. </p>
<p>My null hypothesis is that the regression slopes between x and y is homogeneous across 10 locations (i.e. slopes of y against x is similar across all 10 locations)... | g65273 | [
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<p>I'm doing 10-fold cross validation on a dataset. But in some folds there are edge cases that the denominator in precision-recall calculation is zero (tp + fp =0).</p>
<p>What are the correct values for precision and recall in this case? And what is the correct way of doing cross-validation (should I include these r... | g65274 | [
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<p>I want to compare two different ratios. When this ratio is close to 1 it shows the better stability in the body. Would you please guide me that which statistical test is better for this situation? Please consider SPSS for answering this question.</p>
<p>Here is some information about my situation:
My study was cond... | g65275 | [
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<p>I want to investigate how people (lets say smokers and non-smokers) differ in various characteristics. So I want to perform a binary logistic regression with SPSS. However, my event rate is very low (number of events = 27 and number of non-event = 200). I want to include several predictors: 3 factors, which I gained... | g725 | [
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<p>I have some weekly data about Apple app store ranking of the top apps listed (also of the sub categories such as games, weather, etc.). For example: </p>
<pre><code> week1 week2 week3 week4 ...
Angry Birds 15 13 1 5 ...
Weather Pro ...
</code></pre>
<p>I am thinkin... | g65276 | [
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<p>I have dataset with assumption that nearest neighbors are best predictors. Just a perfect example of two-way gradient visualized- </p>
<p><img src="http://i.stack.imgur.com/7frrm.jpg" alt="enter image description here"></p>
<p>Suppose we have case where few values are missing, we can easily predict based on neighb... | g65277 | [
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<p>I have a presumably simple question. What does this mean: with probability 0.3 variable X is simulated as </p>
<blockquote>
<p>X~N(0,1).</p>
</blockquote>
<p>How can I simulate X using this?</p> | g65278 | [
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<p>How do computers achieve randomness if they really do ?</p>
<p>How to decide whether something is random or not?</p>
<p>Is there a measure of randomness?</p>
<pre><code> Thanks in advance..
</code></pre> | g65279 | [
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<p><a href="http://code.google.com/p/lasso4j/" rel="nofollow">Lasso4j</a> is a Java implementation of the Lasso L1-constrained fitting for linear regression.</p>
<p>I would like to add a non-negativity constraint on the weights, meaning that the non-zero sparse coefficients should be positive.</p>
<p>Is there an easy... | g65280 | [
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<p>I have a problem to classify my data that can fit into more than one class at same time. Based on an initial study, I came across "Multi-label classifier" that can classify data into more than one class simultaneously. Or as its internal implementation goes, I can have multiple single-label classifiers.</p>
<p>I'm ... | g65281 | [
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<p>I currently have a modelling issue, specifically in determining how to code the 'time' factor in my analysis, when the DV has already been adjusted for age.</p>
<p>My DV is a measure of child development, and it has already been adjusted for child age to produce a <em>z</em>-score. Conversion is not linear as the a... | g65282 | [
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<p>I am trying to match individuals based on monthly consumption and geographic consumption in a dense metro area. Essentially I want to create treatment and control pairs with the having both geo location and consumption (total consumption and consumption pattern) as close to the treatment as possible. At first I wa... | g787 | [
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<p>I've got an intuitive block with this. For a binomial problem, the standard deviation of a count is $\sqrt{np(1-p)}$. Conversely, the standard deviation of the sample proportion decreases with increasing $n$ and is $\sqrt{\frac{p(1-p)}{n}}$. I can do the division by $n$ but I don't have a feel why standard deviatio... | g65283 | [
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<p>When reading the topic modeling tutorial written by Blei, <a href="http://www.cs.princeton.edu/~blei/kdd-tutorial.pdf" rel="nofollow">KDD 2011 tutorial</a> I was confused about a set of diagrams which aim to show the effect of $\alpha$ in Dirichlet distribution.</p>
<p>For example, for the plot with $\alpha=1$, wha... | g23792 | [
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<p>I frequently use this formula to compare two positive numbers $x$ and $y$ to see if they are "more different" than some threshold:</p>
<p>$$
x-y \over \max(x,y)
$$</p>
<p>It is nice because it is symmetric and bounded to $[-1,1]$ (unlike relative percent difference). I call it a "symmetric percent difference." I s... | g16896 | [
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<p>I was learning some probability basics. I am stuck with a problem, that I need your help with in solving.</p>
<p>An $e$-fair coin is a coin with probability of head $(\theta)$ in interval $[\frac{1}{2}-e,\frac{1}{2}+e]$. For a Bayesian analysis of the question whether a given coin is $e$-fair, we may assume a unifo... | g3515 | [
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<p>I would like to know what is the difference between Intrinsic dimension and correlation dimension. Searching results say the intrinsic dimension = number of variables used to specify the system in euclidean space. So, what is then correlation dimension? I am aware that correlation dimension is a type of fractal dime... | g16898 | [
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<p>Suppose $X_1,\ldots,X_n$ are random samples of a $U(0,\theta)$ distribution. If $Y_n$ are the largest order statistics of the sample, and $V=\displaystyle\frac{n\bar{X}}{Y_n}$, how can I calculate the probability density function of $V$?</p> | g23797 | [
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<p>We have route-level data (that I cannot share) on monthly bus ridership in New York City, creating a panel $N= 185$, $T=36$. We estimate a fixed effects model and random effects model with R's <code>plm</code> package. (For this MWE, I use the <code>Grunfeld</code> investment data, which illustrates the problems I a... | g23798 | [
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<p>Why is it so common to obtain maximum likelihood estimates of parameters, but you virtually never hear about <em>expected</em> likelihood parameter estimates (i.e., based on the <em>expected value</em> rather than the <em>mode</em> of a likelihood function)? Is this primarily for historical reasons, or for more subs... | g65284 | [
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<p>I have a data set that includes life quality indices for many cities. I want to aggregate the indices to the metropolitan level. Since some cities in each metro area are missing, the data set provides a weighting variable, which was calculated based on the inverse of the probability of a city being in a metropolitan... | g65285 | [
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-0.018872803077101707,
-0.09193684160709381,
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0.06124885007739067,
-0.03913307189941406,
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0.05709042400121689,
-0.015850843861699104,
0.025354592129588127,
0.04028759524226189,
0.00... |
<p>I have firing-rate data for neurons ranging from 40-60 in number for various experimental groups. I've seen both mean and median being used in the literature, but without much explanation for the choice. My boss thinks that usually for sample sizes > 4-5, mean is ok to use. But I would like to have a better justific... | g211 | [
-0.0017300051404163241,
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... |
<p>Birth interval means time between successive births. I have a birth interval data from DHS survey. If we want to see the effect of familial and socioeconomic co-variates on birth interval. How can we see this? What types of statistical models can be used? </p> | g65286 | [
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<p>I have a question regarding the use of the dlm CRAN package for forecasting values of a seasonal time series.</p>
<p>I've built a dlm model combining a stochastic local level model with a stochastic trigonometric (Fourier representation) seasonal component of period 96 (measurements every 15 mins with a daily cycle... | g726 | [
0.018639229238033295,
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0.037790872156620026,
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<p>I'm trying to understand the calculations behind the centroid method of cluster analysis in SAS's <code>PROC CLUSTER</code>. I am able to calculate the reported distances at each join when I set the options to <code>method=centroid nonorm</code>, but I am unable to figure out how the reported distances at each join ... | g65287 | [
0.03502310812473297,
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<p>I'm conducting a meta-analysis on two genome wide association studies (GWAS), each consisting of 150 SNPs, for which I computed summary statistics for association.
I'm using the R package <a href="http://cran.r-project.org/web/packages/meta/index.html" rel="nofollow">meta</a> and the function <code>metagen</code>.
I... | g65288 | [
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<p>What is the range of attainable correlations for the pair of exponentially distributed random variables $X_1 \sim {\rm Exp}(\lambda_1)$ and $X_2 \sim {\rm Exp}(\lambda_2)$, where $\lambda_1, \lambda_2 > 0$ are the rate parameters?</p> | g65289 | [
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<p>Does every Ordinary Least Squares (OLS) regression model have to pass both the Pregibon Test for Linearity (sometimes called link-test) and the Ramsey RESET tests?</p>
<p>I am working on an OLS model and it passes the Pregibon test when I include all the variables I wanted without squared terms. However, it fails t... | g43767 | [
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<p>Let's say we have a RxC contingency table, with R=C. How could one best repopulate the table such that:</p>
<ol>
<li>all counts reside in the off-diagonal cells (zero's on the diagonal);</li>
<li>marginal frequencies remain the same;</li>
<li>the value of Chi square is maximal.</li>
</ol>
<p>I can imagine a very '... | g23803 | [
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<p>I was reading about BATS (Box-Cox transformation, ARMA errors, Trend and Seasonality) and TBATS (Trigonometric, Box-Cox transformation, ARMA errors, Trend and Seasonality) models. I was wondering whether it's possible to get better forecasts with simpler models like standard Holt Winters than using BATS or TBATS?<... | g65290 | [
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<p>I'm running a negative binomial regression to test the intensity of violent events in a given location. One of my X variables has a negative beta coefficient (BC), however the hypothesis behind that variable is a 'negative decline in X contributes to a positive chabe in voilence'. My X variable is vegetation cover ... | g65291 | [
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<p>Hadley Wickham wrote a stellar article called "Tidy Data" (<a href="http://vita.had.co.nz/papers/tidy-data.pdf" rel="nofollow">link</a>) in JSS last year about data manipulation and getting the data into an "optimal" condition in order to perform analysis. However, I was wondering what were best practices in terms o... | g23806 | [
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<p>I have two types of missing data (non-responses and "Don't know or does not apply") and I want to replace only the non-responses (with mean or by using EM or by using Multiple Imputation) and to see if this is a good solution. How can this be done in SPSS? Even in the simplest case, when replacing missing values wit... | g4449 | [
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<p>I suspect that a given coin is not fair, i.e that the probability of heads is not $\frac{1}{2}$. My question is not how we can prove the unfairness, but if we derive a test to check the fairness, How we can evaluate the test?</p>
<p>Say, for $n$ number of tosses, the coin always turned up heads. What is the minimal... | g65292 | [
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<p>I would be really thankful for any hint</p>
<p>Let $x_1,\dots x_n$ be a sample from a geometric distribution with probability parameter $\theta$</p>
<p>$f(x_i\mid \theta)=\theta(1-\theta)^{x_i}$</p>
<p>The likelihood is given by $L(\theta\mid x_i, \dots, x_n)=\prod_i f(x_i\mid \theta)$
Assume we have observed a s... | g65293 | [
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<p>Consider a population of independent light bulbs with an exponential
lifetime distribution with mean $\mu$. It is claimed that their expected
lifetime is 1000 hours. A definition of a <strong>100(1−)%</strong> confidence interval
obtained from an observation t0 is the set of all $\mu_0$ which are not rejected
in a t... | g65294 | [
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... |
<p>Given a two categorization problem, why Bayesian error is concave down as a function of prior $P(w_1)$?</p>
<p>$w_1$, $w_2$ are two underlying concepts with prior $P(w_1)$ and $P(w_2)$. We observe the evidence $x$, which is related to $w_1$ and $w_2$ through conditional probability $p(x|w_1)$ and $p(x|w_2)$.</p>
<... | g65295 | [
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<p>I have a combinatorics question. Say you have two sequences:</p>
<p>$$X_{1},X_{2},X_{3},\ldots,X_{N_{1}}$$</p>
<p>and</p>
<p>$$Y_{1},Y_{2},Y_{3},\ldots,Y_{N_{2}}$$</p>
<p>How can i pair up elements from the $X$'s with elements of the $Y$'s, such that if I pair up $Y_{1}$ with $X_{3}$, then I can only pair up $Y_... | g65296 | [
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<p>I have data that describes the duration of how long a person views a webpage. This is quite varied and in the context wherein I gathered the data, it was very skewed. People mostly spent short amounts of time in a webpage but sometimes spent a significant amount of time viewing it. I want to discretize the durations... | g23811 | [
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<p>Start with a standard deck of 52 cards in some known order; each card can be tagged with its ordinal position in the deck. </p>
<p>Then apply a random shuffling algorithm (i.e. Knuth's shuffle). </p>
<p>After the shuffle, it is possible for one or more cards to end up in the same ordinal position where they were... | g65297 | [
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<p>Why is $k$ called <em>representor of evaluation</em>?
From the book "Learning with kernels" by Bernhard Schölkopf we have the following lines (page 33):</p>
<blockquote>
<p>$\langle k(.,x),f\rangle = f(x)$, in particular $\langle k(.,x), k(.,x')\rangle = k(x,x')$</p>
</blockquote>
<p>According to the book this i... | g65298 | [
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0.07838611304759979,
... |
<p>This may seem like a rather simple concept, but I'm trying to get an intuitive understanding of why we divide. Common formulas in statistics that use division are the calculation of the t statistic and variance. A less well known calculation in evolutionary biology that uses division is strength of female preference... | g65299 | [
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0.0273... |
<p>"How large must a class be to make the probability of finding two people with the same birthday at least 50%?"</p>
<p>I have 360 friends on facebook, and, as expected, the distribution of their birthdays is not uniform at all. I have one day with that has 9 friends with the same birthday. (9 months after big holid... | g49922 | [
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<p>Suppose we have two variables $x_1$ and $x_2$ and an interaction term $x_1 \cdot x_2$. Suppose we set the family-wide error rate to $\alpha = 0.05$. For the Bonferonni correction, would be look at $\alpha/2$ or $\alpha/3$?</p> | g65300 | [
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... |
<p>The log-likelihood function for logistic function is $$l(\theta) = \sum_{i=1}^m(y^{(i)}\log h(x^{(i)}) + (1-y^{(i)})\log(1 - h(x^{(i)})))$$, where $$h(x^{(i)}) = \frac{1}{1 + e^{-\theta^Tx^{(i)}}}\,.$$ </p>
<p>In order to obtain maximum likelihood estimation, I implemented fitting the logistic regression model usin... | g65301 | [
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0.005413631908595562,
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0.0657704770565033,
0.0514... |
<p>I have a database with the Chilean equivalent SAT for 2010. It shows the highest score achieved by one student that belongs to one school. The scores goes from 100 to 820, and it has been published as a 1-to-100 school ranking. Database also contains several qualitative information of schools (managerial issues, bui... | g65302 | [
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0.01042294... |
<p>I'm having trouble following the derivation of the ridge solutions as a sum of vectors in formula 3.47 of <a href="http://www-stat.stanford.edu/~tibs/ElemStatLearn/" rel="nofollow">The Elements of Statistical Learning</a> on pg. 66. It shows the following:</p>
<blockquote>
<blockquote>
<p>$\mathbf{X}\hat{\bet... | g65303 | [
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0.013363680802285671,
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0.04017716646194458,
0.04201901704072952,
-0... |
<p>I know that these laboratory analysis reports each have a linear regression relationship and two have a positive slope and one has a negative slope. I am taking my first statistics class and want to be able to explain these very well in a research poster I am doing for work. Am I missing any important information? T... | g65304 | [
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0.... |
<p>After running Exploratory Factor Analysis in spss v.17 I deleted 4 measurement items which yielded low factor loadings. Now I want to proceed to Confirmatory Factor Analysis to calculate AVE and CR. My Question is should I repeat the EFA to obtain the new factor loadings after deletion of those 4 variables(items) an... | g38426 | [
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0.002302956534549594,
0.015515049919486046,
-0.00... |
<p>Recall the perceptron algorithm:</p>
<p><em>cycle through all points until convergence</em></p>
<p>$\text{if }\, y^{(t)} \neq \theta^{T}x^{(t)} + \theta_0\,\{\\
\quad \theta^{(k+1)} = \theta^{k} + y^{(t)}x^{(t)}\\
\}$</p>
<p>I was studying a modification to to the update rule such that the new update rule is:... | g65305 | [
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0.07821... |
<p>I'm using lmer to analyse my data, building nested models and using anova() to compare them against each other in an incremental way. Now, I know enough to only test a single term at a time (i.e. only one term changes between model 1 and model 2, so that when I compare them with anova I know what question I am answe... | g65306 | [
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0.030824391171336174,
-0.018856799229979515,
0... |
<p>I wish to model the number of bugs caused by software development. This is intuitively sort of a Poisson process, however it is overdispersed. One thing we can do in this case is to use a negative binomial distribution (because negative binomial approaches Poisson as <code>r</code> gets larger, or because we might t... | g65307 | [
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<p>My data set consists of columns containing universities in the Boston area, and rows containing zip codes. For each university and zip code, there are two data points: number of students in campus housing, and number in non-campus housing. So that's two independent variables <code>(x, y)</code>, and for each such ... | g65308 | [
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<p>I want to compare two groups (vectors) having different lengths to see if their distributions differ considerably. However, when I use <code>chisq.test</code>, I get an error due to inequalities of lengths:</p>
<pre><code>> chisq.test(factor(Group1), factor(Group2))
</code></pre>
<p>results in:</p>
<pre><code>... | g65309 | [
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0... |
<p>I've run a multiple linear regression using standardized Betas and a log-transformed dependent variable; the latter transformation is primarily for better approximating linear regression assumptions but it also produces a nifty interpretation (described below).</p>
<p>Standardized Betas provide the interpretation: ... | g65310 | [
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<p>I want to measure the correlations between ratings on different items of a scale. In my sample, there are multiple data points from the same subjects, for each subject to the same extent. I am able to trace the ratings back to the subject who made them. What is the appropriate correlation measure accounting for thes... | g65311 | [
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<p>I have the following data: feces density of a carnivore species subdivided according to sex. I am looking for appropriate test suggestions.
I have calculated the density according to main habitat types, topography, and road types. To determine if results are statistically significant, I would believe the Friedman`s ... | g65312 | [
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<p>I am trying to use R to do Kmeans clustering and as most people I ran into the challenge of determining when to finish. I have 10,000 items and potentially 10 times of that down the road. My goal is to create a series of clusters with minimal size (e.g. 50 items per cluster) OR reasonably similar items. In other wor... | g65313 | [
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<p>In [1] (Page 31,equation 2.12 ) it is claiming that in a graph which is processed by the junction tree algorithm, the joint distribution of the variables could be found by
$$
p(x_1, ..., x_m) = \frac{ \prod_{C \in \mathcal{C}} \mu_{C}(x_C) }{ \prod_{S \in \mathcal{S}} [\mu_{S}(x_S)]^{d(S)-1} }
$$
In which $d(S)$ ... | g23827 | [
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<p>I have a data frame with several predictors, lets call them <code>pred1</code> through <code>pred3</code>, and a result column. Now I need to specify the right model. I could randomly try:</p>
<pre><code>svm.model <- svm(result ~ pred1+pred2+pred3, data = train)
# or
svm.model <- svm(result ~ pred1*pred... | g23828 | [
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0.02... |
<p>People says soft margin SVM use hinge loss function: $\max(0,1-y_i(w^\intercal x_i+b))$. However, the actual objective function that soft margin SVM tries to minimize is
$$
\frac{1}{2}\|w\|^2+C\sum_i\max(0,1-y_i(w^\intercal x_i+b))
$$
Some authors call the $\|w\|^2$ term regularizer and the $\max(0,1-y_i(w^\interca... | g23829 | [
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<p>I have two measurements of something. You can think of them both as their own curve with known error on each point. They look quite similar, and if I calculate the R2 value it comes out to >0.9. But what I want to be able to calculate is a P value comparing these two curves (i.e., what is the probability that the di... | g65314 | [
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<p>I have some detailed data about the commuting patterns of workers. If I know the following 3 things...</p>
<ol>
<li>The total number of workers commuting from one block to another.</li>
<li>The total # and % of manufacturing-sector workers in the origin block.</li>
<li>The total # and % of manufacturing-sector wor... | g65315 | [
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<p>I'm trying to analyse a survey study in which I'm interested in the way that individual differences between my participants influence how they respond to my stimuli. The stimuli are pieces of writing randomly selected from a large pool of such, and I'm not currently interested in any fixed effects of these stimuli.<... | g27060 | [
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<p><strong>Background</strong></p>
<p>notation: RV= random variable, $\mu=$ mean $m=$ median</p>
<p>Jensen's Inequality considers the relationship between the mean of a function of an RV and the function of the mean of an RV.</p>
<p>If $f(x)$ strictly convex:</p>
<p>$$\mu (f(x)) > f(\mu (x))\mathrm{\hspace{20mm}... | g65316 | [
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0... |
<p>I need to make a simulation to calculate the integral of a pdf $f(x|D)$ over a region $T$.That is, I need to evaluate
$$\int_T f(x|D)\; dx$$</p>
<p>to do this, I just defined the function $g(x)=1$ if $x \in T$ and $g(x)=0$ if $x$ is not in $T$. So the integral that I want to evaluate is
$$\int_{D(f)} g(x)f(x|D)\;dx... | g65317 | [
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-0.... |
<p>I am comparing two sections of a single time series on the date that a policy change has occurred.
How do I compare two ARMA coefficients?
Do I use t test?</p>
<p>Thanks a lot.</p> | g65318 | [
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0.02577805332839489,
0.010944... |
<p>For example, we have an NxP matrix with N rows and P variables. Then we need to calculate a PxP sample covariance matrix. How do I do that?</p> | g23838 | [
0.02005569450557232,
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<p>I'm trying to run a basic gradient descent algorithm with a absolute loss function. I can get it to converge to a good solution by it requires a much lower step size and more iterations than had I used square loss. Is this normal? Should I expect absolute loss to take a longer time to come to a good solution or pote... | g37585 | [
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<p>AFAIK, the model works in a following way:</p>
<p>We have $S$ - all the sentences in our unlabeled copra.</p>
<ol>
<li>choose $N$ (~100000) most popular words from our unlabeled data = $PW$</li>
<li>chose the hyperparameters $d_{dim} \in [50...200]$ - the number of dimensions in our embedding and $w_{size}$ - wind... | g65319 | [
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0.0066901990212500095... |
<p>For the standard Cauchy distribution, do fractional moments exist? If $Y \sim C(1,0)$, is it possible to evaluate $E(Y^{1/3})$?</p> | g65320 | [
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<p>I'm more of a programmer than a statistician, so I hope this question isn't too naive.</p>
<p>It happens in sampling program executions at random times. If I take N=10 random-time samples of the program's state, I could see function Foo being executed on, for example, I=3 of those samples. I'm interested in what th... | g43791 | [
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<p>I have two set of data that are roughly centered around zero but I suspect that they have different tails.
I know a few tests to compare the distribution to a normal distribution, but I would like to compare directly the two distributions.</p>
<p>Is there a <strong>simple test to compare the fatness of tail of 2 d... | g65321 | [
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<p>I have few conceptual questions related to application of chaos in communications. In few application such as radar <a href="http://asp.eurasipjournals.com/content/pdf/1687-6180-2011-2.pdf" rel="nofollow">Chaotic signal reconstruction with application to noise radar system</a>, cryptography, the noise considered is ... | g65322 | [
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<p>Given E(X), E(X^2) and sample size. How do I find Coefficient of Variation?</p>
<p>Variance = E(X^2) - E(X)^2</p>
<p>sd = square root of variance</p>
<p>Coefficient of Variation = sd / E(X)</p>
<p>however, with the values that were given, I can't get the answer I want. I wonder if the above formula is correct.</... | g43799 | [
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<p>I'm attempting to analyse a large chunk of empiric measurements subject to two parametrised transformations. In essence, the functions take 3 'count' parameters - and returns a sequence of floats in each configuration. I'm expecting (hoping) to see some interesting patterns emerge when appropriate parameters are sel... | g65323 | [
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0.01781720481812954,
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0.005518138874322176,
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<p>I'm trying to adopt a solution for long-term electricity annual prices forecasting (depending on past electricity prices, past oil prices, past consumption data, etc.)</p>
<p>I'm considering some solutions:</p>
<ul>
<li>off-the-shelf specific software: Alyuda, Aleasoft, ...</li>
<li>already-built modules of known ... | g65324 | [
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<p>I'm trying to understand how to show the prediction error of a model fit in R using the non-linear least squares function <code>nls</code>. Although there is an argument <code>se.fit=TRUE in the</code>predict.nls` function, the help explains "At present se.fit and interval are ignored." I'm able to calculate the con... | g65325 | [
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<p>I am trying to use pybrain for the first time on 20x20 handwritten digit MNIST data. I keep getting a runtime error when I setup the trainer and I can;t figure out what the problem is?</p>
<p>code:</p>
<pre><code>import sys
import os
from pprint import pprint
import numpy
X = numpy.loadtxt('/Users/enpasant/Octa... | g23846 | [
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<p>Is it true that Multinomial Naive Bayes requires equally by count training data for each class to get best performance?</p>
<p>For example, we forming classifier for three classes - Japan, China, Korea.</p>
<p>For Japan available 500 training data, China - 300, Korea - 100.</p>
<p>So to train Multinomial Naive Ba... | g65326 | [
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<p>Background: We are looking at parental leave in Iceland. We are particularly interested in whether the economic crisis and the resulting changes in parental leave legislation affected the time taken for parental leave. </p>
<p>We have reason to believe that the effect of the crisis / new laws will be different for ... | g23847 | [
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... |
<p>Intuitively, CRLB should decrease with increase of signal-to-noise ratio (SNR). A plot of CRLB (Y axis) and SNR on X axis should be somewhat a decreasing exponential curve. Thus, when the signal has more of information and less noise, CRLB decreases. </p>
<p>I have not found any reference for such a plot, but shall... | g65327 | [
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0.005495382472872734,
0.05007334426045418,
-0.06423218548297882,
0.07791923731565475,
0.024118399247527122,
-0.0430443175137043,
-0.006844426039606333,
-0.02840469405055046,
0.04698951542377472,
0.03048534132540226,
0.032... |
<p>Suppose for each of $p$ symptoms we have a measurement of the degree of severity from $1$ to $5$. We have a dataset $\{(x_i,y_i)\}_{i=1}^n$, where $x_i=(x_{ij},j=1,\cdots,p)$ are the measured severities of the symptoms of patient $i$, and $y_i=0$ or $1$ indicates whether or note patient $i$ has the disease.</p>
<p>... | g23849 | [
0.008108175359666348,
-0.04238893836736679,
-0.0174866933375597,
-0.07356999069452286,
-0.03737213462591171,
-0.003668287768959999,
0.02800602838397026,
-0.0041968259029090405,
0.0019791070371866226,
-0.01634892076253891,
-0.0030684007797390223,
0.05875341221690178,
0.011613346636295319,
-... |
<p>I am attempting to estimate a linear model as:
$$
y = a +bX +e
$$
I have a series of annual returns and I would like to estimate the effect of volatility on losses. My Null hypothesis is that volatility in period $t$ should have no linear relationship with losses in period $t+1$. So in actual fact, my model is:
$... | g65328 | [
0.035734254866838455,
-0.07080719619989395,
0.005869058892130852,
-0.0006829230114817619,
0.0018128686351701617,
-0.03530475124716759,
0.037381742149591446,
-0.01232070941478014,
0.01356494054198265,
-0.04901057854294777,
0.03093678317964077,
0.02861226163804531,
0.02489575557410717,
0.036... |
<p>I am trying to use kNN classifier to perform some supervised learning. In order to find the best number of 'k' of kNN, I used cross validation. For example, the following codes load some Matlab standard data and run the cross validation to plot various k values with respect to the cross validation error</p>
<pre><c... | g23851 | [
0.0015021360013633966,
0.012116082943975925,
0.009702019393444061,
-0.01621302403509617,
0.015490789897739887,
0.005089391954243183,
-0.01428449247032404,
0.033280495554208755,
-0.047106631100177765,
0.005079896189272404,
-0.0046296436339616776,
0.04051564261317253,
0.06315241754055023,
0.... |
<p>I know that GLS estimators only have exact distributions asymptotically, so the efficiency gains in finite samples are not all that clear. But otherwise, I'm struggling on how to attack this discussion.</p> | g65329 | [
-0.015682926401495934,
0.04576343297958374,
-0.000009215750651492272,
-0.035754039883613586,
0.015263956971466541,
-0.08449635654687881,
0.021702343598008156,
0.00837948452681303,
-0.003800680162385106,
-0.0007236372330226004,
0.014681105501949787,
0.030595550313591957,
0.02598845586180687,
... |
<p>I am analysing data of an digital advertising tool. I have access to all the exposures for each of the 6 channels (x1, x2, .., x6) of an online campaign. The outcome is the conversion (y=1 or 0) on the website.
My goal is to calculate an attribution model and credit each of the channels with the number of conversion... | g65330 | [
0.003968089818954468,
-0.023951895534992218,
-0.006308084819465876,
-0.019488196820020676,
0.004693268332630396,
-0.017850760370492935,
0.0292543713003397,
0.0402059443295002,
-0.021964116021990776,
-0.01579967327415943,
0.020058220252394676,
0.015307697467505932,
0.08764950186014175,
0.05... |
<p>As a ML beginner, I don't how to begin with this problem, or more generally, are there any typical steps to take when approaching a real problem? </p>
<p>If I have some domain relevant knowledge, then I could make use of it to analyze the data and do the modelling. But if I don't, then all I have is just the data, ... | g65331 | [
-0.023951314389705658,
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0.018412891775369644,
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0.05071151629090309,
0.05133434757590294,
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-0.04509216174483299,
-0.029252413660287857,
0.027551494538784027,
0.09896593540906906,
0... |
<p>I am working on a data set of intertidal organisms and am looking for a multivariate technique that will help me determine why some groups have different species assemblages than others. I was thinking multivariate analysis of covariance (MANCOVA) might be a good method because it takes care of the experimental desi... | g29113 | [
0.003644655691459775,
-0.039626944810152054,
0.020324498414993286,
-0.07696601003408432,
-0.006481391843408346,
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0.059375252574682236,
0.004667795263230801,
-0.024057330563664436,
0.02568209543824196,
0.06758493930101395,
0.010629616677761078,
0.0153508884832263,
0.066... |
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