question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I want to check whether a group of patients are significantly different from their control group. However, I also want to check if the p-value is still significant in case a covariate is taken into account. For that I created a simple data frame in R:</p>
<pre><code>data <- data.frame(group = c(rep("CTRL", 10), ... | g25796 | [
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<p>For one of my grad school classes I am working on a projection analysis. The data includes projected year-end balances. These balances are projected every month of the fiscal year (starting in July and ending in June) to see how much approximately is the Y-T-D amount going to be. I'd like to analyze the projected ba... | g25797 | [
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<p>I just had a very simple (possibly very dumb) question.</p>
<p>How would I, experimentally prove that two random variables drawn either from the same population or two different populations are independent (or for that matter of fact dependent).</p>
<p>Thanks.</p> | g38005 | [
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<p>In a fuzzy regression discontinuity design, what does the exclusion restriction look like in terms of a conditional expectation between the instrument in the first stage and the error term in the structural equation? </p>
<p>In IV, we normally say that the first-stage must produce a non-zero estimate (and preferab... | g46176 | [
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<p>The ID3 algorithm uses "Information Gain" measure.</p>
<p>The C4.5 uses "Gain Ratio" measure which is Information Gain divided by SplitInfo, whereas SplitInfo is high for a split where records split evenly between different outcomes and low otherwise.</p>
<p>My question is:</p>
<p>How does this help to solve the ... | g66671 | [
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<p>I have a number of timeseries on which I want to apply a PCA (using matlab). These time series have very different variances. </p>
<p>My objective is:
1) all time series have the same weight for me, no one should get overweighted
2) I don't want the nature of my data (statistical properties) to get modified through... | g25800 | [
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<p>I am fitting a logistic regression model using lassoglm in matlab. I issued the following command</p>
<pre><code>[B,FitInfo] = lassoglm(ec50,Y,'binomial','Lambda',0.0001,'CV',10);
</code></pre>
<p>Now once I get the coefficients B, how am I supposed to use it. I mean do I have to do</p>
<p>$P(y=1) = \frac{e^{(\th... | g49757 | [
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<p>I just noticed that the Nelson-Aalen estimate of the cumulative hazard changes depends on the existence of tied events. As a toy example, consider a study with 3 patients. The patients die on day 1, 5, and 14 of the study. If we check the patients status daily, the Nelson-Aalen estimate for the cumulative hazard at ... | g25802 | [
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<p>Have you any idea about implementing 2D object recognition with MATLAB?
Which characteristics of objects can feed a neural network? <br/>
It's <a href="http://www.vision.ee.ethz.ch/datasets/downloads/Obj_DB.tar.gz" rel="nofollow">my training data-set</a> (provided by ETH University of Switzerland) <br/>
What is t... | g66672 | [
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<p>I'd be too happy, if someone could post a code snippet, which explains how to compute mean and variance of a set of records, which contain frequencies?</p>
<p>Suppose we have records like <strong>(FORMAT F)</strong></p>
<pre><code>- GroupA, 6 x Grade 1, 5 x Grade 2, 10 x Grade 3
- GroupB, 2 x Grade 1, 7 x Grade 2,... | g3960 | [
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<p>In a multivariable generalized additive model with Gaussian family and identity link function, in which some explanatory variables are modelled linearly and some are modelled as smooth functions, to what extent is inference on the linear terms analogous to that on ordinary least squares coefficients?</p>
<p>Based o... | g66673 | [
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<p>I want to model the effect of Level (continuous) of different Additives (categorical) on Y (continuous) by fitting a linear model, so my data is going to look like this:</p>
<pre><code>Additive Level Y
A 1 2.3
A 2 4.5
A 3 6.7
<snip>
B 1 8.9
B ... | g66674 | [
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<p>I've got the next question.
Let's consider I have the pair of distributions:
X|t ~ Binomial(n,t); t~Beta(a,b). Here n,a,b are known.
I need to construct conditional probability to sample from it, t|X.
In this example I can do this analytically, t|X ~ Beta(x+a,n-x+b)
But how can I do this in general case, for any dis... | g66675 | [
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<p>I am confused in understanding the formal definition for independence and how does this differ from the law of total expectations.</p>
<p>I thought that $E[u|x]=E[u]$ formally means independence of $u$ and $x$. </p>
<p>However, when I have $E[u|x]=a$ (const) and use the law of total expectations,</p>
<p>$E[u]=E[E... | g117 | [
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<p>I'm trying to apply logistic regression to the data with binary predictor. But some of my variables are numerical and some are categorical. If I just do this in R I get the model where for every categorical variable I have coefficients and p-values for for variable's possible values except for the first.
How can I i... | g25805 | [
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<p>I'm developing a classifier system to detect objects of interest in images. I want to report a score, but I'm a bit lost as to what the most fair and informative number is.</p>
<p>Sensitivity and specificity seem to be commonly used, but while I have numbers for true positive, false positives and false negatives, I... | g25806 | [
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<p>I'm given a $M\times N$ ($M$ rows, $N$ cols) matrix $X$ and a $1\times M$ column vector $y$ ($M>N$). I need to find such a vector $x$ that minimizes the value of s, where</p>
<p>$s= \sum_{i=1}^{M}\left [(y_i - \hat{y}_i)^2 \right] $</p>
<p>and where $\hat{y} = X \times x$</p>
<p>Basicaly, this is a set of linear ... | g66676 | [
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<p>Ratios (X/Y, e.g. body mass index) are variables with odd distributions. They have no means or moments (e.g. variances, skewness or kurtosis). Thus, my questions are:</p>
<ol>
<li>How to compare between (or among) 2 or more groups with ratio variables?</li>
<li>How to use ratio variables as the independent variable... | g25807 | [
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<p>The density of my data set was plotted in R as follows.</p>
<p><img src="http://i.stack.imgur.com/vUUFp.png" alt="enter image description here"></p>
<p>What kind of distribution would fit this data?</p>
<p>As I am not experienced to tell by visualization, I can only guess it is not normally distributed. I shall ... | g66677 | [
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<p><a href="http://en.wikipedia.org/wiki/Stein%27s_example">Stein's Example</a> shows that the maximum likelihood estimate of $n$ normally distributed variables with means $\mu_1,\ldots,\mu_n$ and variances $1$ is inadmissible (under a square loss function) iff $n\ge 3$. For a neat proof, see <a href="http://www-stat.s... | g25808 | [
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<p>I have a dataset containing 10,000 examples with 8 features. I would like to create a random forest to classify this dataset in two classes, more specific: substrate / no substrate. In this dataset there are approx 20 TRUE positives that I got from literature. I would like to predict other potential substrates. I cr... | g3983 | [
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<p>I need to calculate the linear model in R, i did the following: </p>
<blockquote>
<p>summary(model)</p>
</blockquote>
<p>But what if I wanted to calculate only the first point? A bit stuck with this one... Many thanks!
Here is the code used to create plot itself:</p>
<pre><code>> elevation=c(12, 34, 32, 12, ... | g66678 | [
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<p>It is fairly straightforward to calculate the variance of the paired t-test:</p>
<p>$Var(\overline{D})=Var(\overline{Y_1})+Var(\overline{Y_2})-2*Covar[Var(\overline{Y_1})*Var(\overline{Y_2})]$</p>
<p>But how can you calculate this variance if you have at each of the two measurements a number of measurements per pa... | g66679 | [
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<p>I have a data set $Y$, $Y$ is assumed to follow a poisson distribution with mean = $\lambda$ . </p>
<p>However, each element $y_i$ in $Y$ is accompanied with a covariate $x_i$. So here I want to use poisson regression to model this dataset. The link function is assumed to be log($\lambda(i)$)=$\beta_0$+$\beta_1x_i$... | g66680 | [
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<p>I'm using a daily time series of sales data that contains about 2 years of daily data points. Based on some of the online-tutorials / examples I tried to identify the seasonality in the data. It seems that there is a weekly, monthly and probably a yearly periodicity / seasonality.</p>
<p>For example, there are payd... | g46188 | [
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<p>Can any one point me to a research article or post the actual algorithm to generate random numbers from the multivariate normal distribution in spherical coordinates?</p>
<p>I need both $N_p(0,I_p)$ , the standard multivariate normal case in spherical coordinates and $N_p(0,\Sigma)$ where $\Sigma \neq I_p$</p> | g66681 | [
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<p>I'm doing some machine learning and get a set of optimum weights in the end. I'd like to verify that these weights are by and large the same no matter how many times I train on the data. I assume that my cost function has a global minimum.</p>
<p>How can I measure the similarity between two set of weights that I go... | g66682 | [
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<p>I'm reading Luce (1959). Then I found this statement:</p>
<blockquote>
<p>When a person chooses among alternatives, very often their responses
appear to be governed by probabilities that are conditioned on the
choice set. But ordinary probability theory with its standard
definition of conditional probabilit... | g66683 | [
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<p>From my experiment, given training samples of around 600 each having vector length of 30, the single gaussian component performed much better unexpectedly. Having said that, I want to know how or when it is better to use mixture of Gaussian (any rule of thumb or whatever)</p> | g66684 | [
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<p>So I've been trying to make sense of the clustering algorithm on page 6 of <a href="http://www.kyb.mpg.de/fileadmin/user_upload/files/publications/attachments/Luxburg07_tutorial_4488%5B0%5D.pdf" rel="nofollow">this paper</a>. </p>
<p><img src="http://i.stack.imgur.com/wE9PB.png" alt="Algorithm"></p>
<p>Are the "f... | g17183 | [
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0.08847904205322266,
0.... |
<p>I'd like to understand the use of Monte Carlo simulation in the <code>chisq.test()</code> function in R.</p>
<p>I have a qualitative variable which has 128 levels / classes. My sample size is 26 (I was not able to sample more "individuals"). So obviously, I will have some levels with 0 "individuals". But the fact i... | g66685 | [
-0.0016190047608688474,
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0.005533900111913681,
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0.019022049382328987,
... |
<p>Is there an R package or other open source software that solves the problem of inferring the parameters of a <a href="http://en.wikipedia.org/wiki/Linear_congruential_generator" rel="nofollow">linear congruential generator</a>?
Such inference can be done as e.g. described <a href="http://www.reteam.org/papers/e59.pd... | g66686 | [
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0.0... |
<p><strong>Background:</strong> I have developed a logistic regression model where I am trying to analyze the effect of socio-economic data of a family on their probability of receiving a home loan. I have used fractional polynomials to achieve linearity in my continuous covariates. One such variable is "disposable inc... | g66687 | [
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0.036452025175094604,
0.01376382727175951,
-0.024... |
<p>I'm currently a web developer with a backgound mainly in server side technologies however I've always had an interest in probability so recently I've been exploring building a dummy betting platform where people wager against insurance policies and essentially I'm aiming to use data from Google's index to set the od... | g459 | [
0.02156464010477066,
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<p>I am trying to estimate a random parameter linear regression models in <a href="http://www.limdep.com/" rel="nofollow">LIMDEP</a> (Hildreth, Houck and Swamy's Random Coeffficents Model). Since my data is x-sectional, therefore, I am not using Pds command (being x-sectional data), my commands are as follows:</p>
<pr... | g37511 | [
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0.03171199932694435,
0.01... |
<p>I am reading Applied Logistic Regression by Hosmer and Lemeshow.</p>
<p>In chapter 1, they defined $D$ as $-2\ln(\text{likelihood ratio})$, which $D$ is also known as the <em>deviance</em>, and $G$ as
$$D(\text{model without the variable}) - D(\text{model with the variable}).$$</p>
<p>I wonder if $G$ also has an ... | g46198 | [
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-0.0... |
<h3>Context</h3>
<p>When I teach students about the correlation coefficient, I like to give students a sense of how correlations map on to common associations that might be encountered in daily life and across various topics and disciplines.</p>
<p>Some years back I read a psychology journal article (it might have b... | g37472 | [
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<p>I have been performing a relatively routine fit on data for some time. I fit the data to a fairly simple semi-empirical function. For each data point I perform repeated experiments to build a histogram and then fit using standard methods.</p>
<p>However the situation is slightly more complicated than this, technica... | g25816 | [
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<p>Say $X_0, X_1, ...$ is a Markov chain with the state space is $S=\{0,1,2,3,...,N-1\}$ and the transition probability $P(X_{n+1}=a+1 \mod N | X_n=a)$ = $P(X_{n+1}=a \mod N | X_n=a)$ = $P(X_{n+1}=a-1 \mod N | X_n=a)$ = $1/3$. (Ie, the markov chain is a random walk on $S$ with 1/3 probability of staying put, 1/3 pro... | g66688 | [
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0... |
<p>I have a timecourse dataset consisting of 3 groups of patients as follows:</p>
<p>Group1: control </p>
<p>Group2: Medication A to reduce pain after a medical procedure</p>
<p>Group3: Medication B to reduce pain after a medical procedure</p>
<p>I will like to find out if there are differences between the groups. ... | g66689 | [
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0.010408277623355389,
0.020058896392583847,
0.... |
<p>I have a statistical question about a project I recently got.
We performed a flow cytometry assay on 3 different groups: controls (n=5), patients before treatment (n=5) and paired patients after treatment (n=5).</p>
<p>My plan would be to compare the median expression of the same cell population in controls and pat... | g66690 | [
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0.020806487649679184,
0.00007699379784753546,
0.023918215185403824,
0.0134714236482977... |
<p>I would like to understand how can I check if some points around a line have constant distance between the point and the line.</p>
<p>So image a normal chart(cartesian plane) with a line that is formed with points where its coordinates are: x > 0 and y > 0 so always numbers bigger then zero.</p>
<p>Then, when I ha... | g17186 | [
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<p>I'm a CS major and don't quite understand the mathematics behind a optimization problem coming from a machine learning algorithm. The algorithm is in Section 5 of the paper <a href="http://visl.technion.ac.il/bron/publications/BroBroOvsGuiTOG10.pdf">http://visl.technion.ac.il/bron/publications/BroBroOvsGuiTOG10.pdf<... | g66691 | [
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<p>I am planning a two arm study (a treatment group and a control). My endpoint is a continuous variable. Every patient will give between 1 to 3 samples, from different locations in the body. Most of the patients will give either 1 or 2 samples, only a minority will give 3.</p>
<p>I know how to calculate a sample size... | g35515 | [
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0.01208038255572319,
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0.03856917843222618,
-0.011598674580454826,
... |
<pre><code>factanal(x = ~V1 + V2 + V3 + V4 + V5, factors = 2, data = airfoil_self_noise)
Uniquenesses:
V1 V2 V3 V4 V5
0.898 0.005 0.005 0.995 0.394
Loadings:
Factor1 Factor2
V1 -0.319
V2 0.877 -0.474
V3 0.997
V4
V5 0.754 -0.194
</code></pre>
<p>Here, I hav... | g66692 | [
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-0.02437375672161579,
-0.056630633771419525,
0.034025661647319794,
0.029956325888633728,
0.0133... |
<p>F-score can be used to measure the discrimination of two sets of real-numbers and can be used for feature selection. However, I once read that </p>
<blockquote>
<p>A disadvantage of F-score is that it does not reveal mutual information among features. </p>
</blockquote>
<p>How to understand this statement, or wh... | g66693 | [
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0.0423711... |
<p>I was reading <a href="http://www.thespec.com/news/ontario/article/646092--aries-most-arrested-sign-by-chatham-police-this-year" rel="nofollow">this article</a>, and wanted to check whether 203/2000 was statistically different from 1/12. Is this a comparison between two means? How can I do this without knowing the s... | g4130 | [
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0.03664277866482735,
... |
<p>Is it, in general, possible that two variables are endogenous even if they are not correlated with each other at all?</p> | g66694 | [
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0.0... |
<p>I am here to seek opinion on how should i represent my data that i have collected. I am to create a presentation focusing on environment. I was told that a simple bar chart and a line graph is a bad visualization </p>
<p>I have picked the following data set as a start</p>
<ul>
<li>Carbon dioxide emission</li>
<li>... | g66695 | [
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0.006348757538944483,
0.08745622634887695,
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0.07911062240600586,
0.028... |
<p>I have a set of general conditions A, B, C, D, E and F to solve a problem. Each of these conditions lead me to different number of experiments according to a parameter that i change in each general condition:</p>
<ul>
<li>condition A has 6 experiments</li>
<li>condition B has 24 experiments</li>
<li>condition C has... | g66696 | [
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0.011409464292228222,
0.05508990213274956,
0.010712006129324436,
-0.025080200284719467,
0.0... |
<p>I read quite a bit of hidden Markov models and was able to code a pretty basic version of it myself.</p>
<p>But there are two main ways I seem to learn. One is to read and implement it into code (which is done) and the second is to understand how it applies under different situations (so I can better understand how... | g37960 | [
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-0.005712985992431641,
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0.012903256341814995,
0.06560761481523514,
0.022... |
<p>I have 2 samples, which I got by conducting a 5-point Likert scale survey. I have 9 results for group A and 17 results for group B for 12 variables. I would like to test now if the groups differ significantly in one or more of these variables and chose to employ the t-test. Assumptions for the t-test are 1. Interval... | g25835 | [
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... |
<p>I have a hypothesis such as "People consult internet before making a purchase decision" for a thesis research. In order to test it, I created a game where people had the option to consult "internet option" or not. I have a similar questions, but I have now realised that all my variables for this particular point are... | g66697 | [
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0.03567977994680405,
0.07494275271892548,
0.007148991338908672,
0.006074980832636356,
0.... |
<p>I am trying to train a Naive Bayes classifier. In addition to getting the most likely class as an output from the Naive Bayes classifier, I would also like to compute the probabilities associated with labels.</p>
<p>I am making two assumptions: 1) conditional independence of features given the class label, and 2) i... | g66698 | [
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-0.05184875428676605,
0.023877428844571114,
0.05742809176445007,
0.06301753968000412,
0.0693... |
<p>I am really new to R and to time series. My field of studies is in the field of Networks and Telecommunication, but my summer internship is about trying to find a statistical model for some sets of data.</p>
<p>The data consists of what is called "10-minutes-points", recorded over a year and which represent power c... | g66699 | [
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0.023284204304218292,
0.021553773432970047,
0.06627156585454941,
-0.0344... |
<p>I have a data set containing two variables <code>x</code> and <code>y</code>. I want to estimate the parameters for a regression model. </p>
<p>The regression model is:</p>
<p><img src="http://i.stack.imgur.com/hsL5M.png" alt="enter image description here"></p>
<p>The maximum likelihood function that estimates th... | g25838 | [
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0.04083169996738434,
-0.054267413914203644,
0.01612205058336258,
0.029569970443844795,
0... |
<p>I'm trying to figure out, how to best deal with an "other" group or how to create one. I'm using R and ggplot2.</p>
<h1>Data</h1>
<p>As an example: I'm analyzing the german Bundestagswahl (general election, every four years). There are at least 38 parties, that voters could vote for in 2009 (see <a href="http://ww... | g27972 | [
0.003161729546263814,
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0.02903715893626213,
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-0.014700817875564098,
0.038679514080286026,
0.03210824728012085,
0.033050987869501114,
0.0... |
<p>I have a model where the $y$ is very skewed and I convert it to log and run a log linear model.</p>
<p>But, I have doubts about the way to measure the error, because in the original variables the error would be much bigger than in log variables. Are there any other ways to measure the error?</p>
<p>I would prefer ... | g66700 | [
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0.028857337310910225,
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0.027409132570028305,
0.04378384351730347,
0.... |
<p>Question that seems complex but probably isn't. </p>
<p>I'm comparing 10 metagenomes (http://en.wikipedia.org/wiki/Metagenomics), that are supposedly unrelated (they are 10 geographically separate locations), for a specific group of operons (http://en.wikipedia.org/wiki/Operon). I'm using Hidden Markov Model protei... | g25843 | [
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-0.027527691796422005,
0.003746024565771222,
-0.010718286968767643,
0.04301673546433449,
0... |
<p>Imagine some paired data ${(x_i,y_i)}_{i=1}^n$ representing the results of two different measurement methods and the question is about the quantification of the bias between the two methods. Let us assume that the normality assumption is reasonable for $x_i-y_i$ hence we simply compute an estimate and a confidence i... | g66701 | [
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0.031676776707172394,
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-0.001840393291786313,
0.03602273017168045,
0.04434851557016373,
0.0005641127354465425,
... |
<p>I ran a simple randomized experiment with 1 control and 1 experimental condition (final N = 80). The dependent variable (frequency of a shown behavior) is clearly not normally distributed so I thought about bootstrapping my analysis (an independent t-test).</p>
<p>The t-test <em>without</em> bootstrapping resulted ... | g25845 | [
-0.0032604301813989878,
0.016442064195871353,
-0.0008169119828380644,
0.019894346594810486,
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0.029841125011444092,
0.019208362326025963,
0.04180102422833443,
0.0... |
<p>How can a random forest model be published so that it also can be externally validated? Is it possible to get an average of the node split values from the ensemble?</p> | g46179 | [
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0.041047342121601105,
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<p>In circular statistics, the expectation value of a random variable $Z$ with values on the circle $S$ is defined as
$$
m_1(Z)=\int_S z P^Z(\theta)\textrm{d}\theta
$$
(see <a href="http://en.wikipedia.org/wiki/Circular_statistics#Moments" rel="nofollow">wikipedia</a>).
This is a very natural definition, as is the defi... | g66702 | [
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<p>In an average (median?) conversation about statistics you will often find yourself discussing this or that method of analyzing this or that type of data. In my experience, careful study design with special thought with regards to the statistical analysis is often neglected (working in biology/ecology, this seems to ... | g37460 | [
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<p>I am working with a large data set (approximately 50K observations) and trying to running a Maximum likelihood estimation on 5 unknowns in Stata. </p>
<p>I encountered an error message of "Numerical Overflow". How can I overcome this? </p>
<p>I am trying to run a Stochastic Frontier analysis using the built in Sta... | g66703 | [
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<p>I am trying to compare it to Euclidean distance and Pearson correlation</p> | g66704 | [
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<p>I want to predict the results of a simple card game, to judge on average, how long a game will last.</p>
<p>My 'simple' game is;</p>
<ul>
<li>Cards are dealt from a randomised
deck to n players (typically 2-4)</li>
<li>Each player gets five cards</li>
<li>The top
card from the deck is turned over</li>
<li>Each pla... | g46245 | [
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<p><strong>Given an easily-computable probability density function $f(x)$, what algorithm can we use to numerically approximate percentiles?</strong></p>
<p>For instance, we might be looking for $x$ such that given $X \sim f(x)$, $p(X \le x) = 95\%$.</p>
<hr>
<p>Here is a use case that motivates this:</p>
<p>We're ... | g66705 | [
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<p>I have a rather simple question (I hope) but for some reason I can't find the right/ a working answer anywhere on the web.</p>
<p>For my research I have measured mood on a scale 1-10, 6 times a day for 5 weeks. (thus a repeated measures design if i am not mistaken). The participants were assigned to three condition... | g159 | [
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<p>I want to perform a Kruskal-Wallis test, but I can't figure out whether this test will automatically rank my data or whether I have to rank it myself before I run the test.</p> | g66706 | [
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<p>I want to calculate the required sample size for a call centre with a finite population.</p>
<p>The survey will collect data on many variables. The objective is to gain data about a range of psychological aspects as well as durations, agent performance, call resolution etc. Therefore I cannot choose a sample size a... | g25853 | [
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<p>Currently I am using SVM to perform some classification task. I use libSVM with Matlab interface. From the practical guide of SVM (<a href="http://www.csie.ntu.edu.tw/~cjlin/papers/guide/guide.pdf" rel="nofollow">Link</a>), we know that there are two parameters need to be tuned, namely L and C. L is the lambda param... | g66707 | [
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0.027189206331968307,
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0.0387144573032856,
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0.043... |
<p>I am trying to determine the key drivers from a series of 30 Independent Variables (IVs) (attributes rated on 10 pt scale) on 3 Dependent Variables (DVs) (i.e. purchase intent). The 30 IVs are pretty highly correlated, but the Variance Inflation Factors (VIFs) are all under 10 (though most are over 5). I did a backw... | g46249 | [
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0.04708190634846687,
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<p>I have transition matrix for the Markov chain of large size. Each entry of the matrix involves some complicated summations and products. </p>
<p>I would like to find stationary distribution and analyze some other parameters the system. </p>
<p>Is there any way to do the above tasks in simpler manner. </p> | g66708 | [
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0.00022503770014736801,
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<p>I have a dataset depicting weekly revenue over time for a computer company. The plot for the data looks like this:</p>
<p><img src="http://i.stack.imgur.com/DDoy8.png" alt="enter image description here"></p>
<p>I decomposed the data into its additive components using the <code>decompose</code> function in R and pl... | g66709 | [
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<p>I was proposed a problem and I am not quite sure how to go about it. The problem is I want to find a relationship between two variables. For the simplified case there are only two variables, lets say Diabetes and Congestive Heart Failure. Each variables has a $0$ or a $1$, if you do not have the disease or if you do... | g66710 | [
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0.04334811866283417,
0.048338472843170166,
0.06977211683988571,
0.01... |
<p>Suppose I have $k$ outcomes with probabilities, $p_i$, with $p_1+p_2+\dots+p_k=1$. Each probability has the same distribution. What would the distribution of a sum of probabilities be? For example, what would the distribution of $p_1+p_2$ be? The Irwin-Hall distribution is the distribution for the sum of uniformly d... | g25857 | [
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0.... |
<p>I have a huge data set that looks roughly like this:</p>
<pre><code>x = [x1, x2, x3, ..., x800]
x is how much percent the real project cost is different from the planned project cost
y1 = [y1.1, y1.2, y1.3, ..., y1.800]
y1 is the estimated project cost in dollar (or another currency)
y2 = [y2.1, y2.2, y2.3, ..., ... | g66711 | [
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0.006607127841562033,
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0.0061200461350381374,
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-0.0029944886919111013,
0.023389456793665886,
0.002240212168544531,
0.06808239221572876... |
<p>I'm trying to calculate a bivariate normal distribution in matlab(with mvnpdf),
but the pdf I obtain has a strange shape with several peaks.</p>
<p><img src="http://i.stack.imgur.com/vMLuj.png" alt="Results obtained"></p>
<p>This is the code I use:</p>
<pre><code>s=[3,1]';
C_ee = [0.0473 -0.1446;
-0.144... | g25858 | [
0.027472764253616333,
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0.0561724416911602,
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0.012286298908293247,
0.024354541674256325,
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-0.005868918728083372,
0.02654714323580265,
0.041957780718803406,
0.04582453891634941,
-0.... |
<p>Suppose $x_{t} = w_{t} + \theta w_{t-1}$ where $w_t$ is white noise with variance $\sigma_{w}^2$</p>
<p>Derive the minimum mean square error one-step forecast based on the infinite past and determine the mean square error of this forecast.</p>
<p>Let $\tilde{x}_n^{n+1}$ be the truncated one step ahead forecast bas... | g66712 | [
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0.06461251527070999,
0.025363966822624207,
0... |
<p>I have a problem..</p>
<p>I'm trying to create a multiclass SVM with probability output. The SVM is working so far, what means, that the accuracy is ok (see the last picture). But the probability estimation does not work so far.</p>
<p>I use the one vs one multiclass encoding.
Now as Platt (<a href="http://en.wiki... | g25859 | [
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0... |
<p>I'm very new to this area and am having difficulty understanding the concept of rejecting the null hypothesis based upon results from the ANOVA table. How do the calculated F and the critical value relate to the p-value? And if the calculated F is greater than 1, does that always indicate that the null hypothesis ... | g46255 | [
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0.014592894352972507,
0.06690336763858795,
0.045397... |
<p>I'm using the <code>lme4</code> package in R to do some logistic mixed-effects modeling.<br>
My understanding was that sum of each random effects should be zero.</p>
<p>When I make toy linear mixed-models using <code>lmer</code>, the random effects are usually < $10^{-10}$ confirming my belief that the <code>col... | g46256 | [
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0.007614064961671829,
-... |
<p>I'm looking for a quick (event if not so accurate) way to deal with over-sampled curves using R. Consider the following example in which <code>x</code> contains 1000 values in the range [0, 1) and <code>y</code> is some function of <code>x</code>.</p>
<pre><code>x <- sort(runif(1000))
y <- sin(x)
</code></pre... | g66713 | [
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0.004202673211693764,
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0.04201600328087807,
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<p>I'm working on a problem where I need to find the probability of a given data sample belonging to a give class using the Bayes Theorem for classification. </p>
<p>From everything I've been able to find so far the way to do this would be to first calculate the conditional probabilities using multivariate Gaussians (... | g66714 | [
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0.05504337325692177,
0.037721727043390274,
0.020469985902309418,
0.025... |
<p>I have a set of 10 variables (v1..v10) which are continuous. I have another two control variables ctrl11 and ctrl12 which of course are categorical. ctrl11 can take any values from 1 to 50 and ctrl12 can take any value from 1 to 200. </p>
<p>I am trying to shrink ctrl11 and ctrl12 to about 5-10 categories rather th... | g66715 | [
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0.005359307397156954,
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0... |
<p>I was thinking of devising a clustering algorithm (for fun and kicks) that would cluster data by looking at the distribution of the data at multiple scales.</p>
<p>For example say my data was distributed on a 2d grid of 1000 x 1000.</p>
<p>Are there algorithms out there that cluster this data by looking at the dat... | g66716 | [
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... |
<p>There are 10 datasets, each contains around 2000 records with 21 features and a binary label.<br>
There have been many attempts to clean the data and even showing that there were so many redundant, duplicate and almost identical records in the original version of dataset.</p>
<p>In all versions of cleaned data, mor... | g4 | [
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0.033102910965681076,
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0... |
<p>I am using 10 fold cross validation using the <code>CVlm()</code> function from the DAAG package. This is part of the result shown:</p>
<pre><code>Predicted 2.47e-04 2.26e-04 -0.000359 0.000335
cvpred -7.88e-05 3.72e-06 -0.000597 0.000322
y 1.47e-03 2.21e-03 -0.004676 -0.001969
CV residual ... | g66717 | [
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-0.01941230520606041,
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0.056180134415626526,
0.060470595955848694,
... |
<p>I have 6 age groups 18-20, 20-30, …, >60. I want to see the significant association between age and no. of hypertensives. I used Chi-square test for this and I found significant. Now can I compute odds ratio to each group so that to get in which age group risk is more? If I can use OR how to do it ? </p> | g66718 | [
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0.... |
<p>Currently I am working on multivariate outlier detection. I would like to try some statistical methods, such as the Minimum Covariance Determinant (MCD) method, to identify the outliers.</p>
<p>In my data set, some of the variables do not follow certain distributions, say the Gaussian distribution. Therefore, I am ... | g66719 | [
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<p>I am learning Gibbs Sampling, in which there is a step named sampling from conditional distributions. I don't understand:
1. where is the conditional distribution from? From a general case, how can I get the conditional distribution? </p>
<p>Any help will be greatly appreciated. </p> | g25866 | [
0.05776648223400116,
0.010438023135066032,
0.014854662120342255,
-0.05023898184299469,
0.019028382375836372,
0.009484130889177322,
-0.028108570724725723,
0.06697162985801697,
0.025997735559940338,
-0.06812229752540588,
-0.005741402972489595,
0.006479504518210888,
0.0536772757768631,
-0.023... |
<ul>
<li><p>n=6 (this relates to maximum values of measurements of force (in Newton) when conducting the same process with the same setting of parameters 6 times)</p></li>
<li><p><a href="http://office.microsoft.com/en-us/excel-help/confidence-norm-function-HP010335675.aspx" rel="nofollow">There is <code>CONFIDENCE.NOR... | g66720 | [
0.05344279110431671,
-0.03243565931916237,
-0.020406363531947136,
0.006563153583556414,
0.027466073632240295,
0.015332117676734924,
0.02110552042722702,
0.008256656117737293,
-0.08598599582910538,
-0.010271177627146244,
-0.006884596310555935,
-0.0035643537994474173,
0.03949807584285736,
0.... |
<p>I have two sets of data, say sales and profit, and I have calculated the correlation between these two data over different months using <code>R</code>. So currently I have somethings like this:</p>
<pre><code>Month | Jan | Feb | Mar | Apr | ....
sales | X | Y | Z | P | ....
profit | A | ... | g25867 | [
0.03207850828766823,
-0.04143255949020386,
0.022322744131088257,
0.009495367296040058,
-0.04034557193517685,
-0.01577162556350231,
0.07160762697458267,
0.002832175465300679,
-0.013155873864889145,
-0.07227052748203278,
0.005586165934801102,
0.012699178420007229,
0.061870213598012924,
-0.01... |
<p>I ran two logistic regression models, one with a dataset including outliers and one without outliers, with multiple predictors.</p>
<p>I checked each model's fit with the le Cessie – van Houwelingen – Copas – Hosmer unweighted sum of squares test for global goodness of fit from the rms package in R (following advic... | g25868 | [
0.008540434762835503,
-0.06565406173467636,
0.026650406420230865,
0.012150505557656288,
0.014217313379049301,
0.03630505129694939,
0.017872298136353493,
0.012825229205191135,
-0.046777646988630295,
-0.006315899547189474,
0.046510495245456696,
-0.00202211644500494,
0.046021416783332825,
-0.... |
<p>I'm using ridge regression for estimating the fair value of variable $Y$ against a vector of correlated predictor variables $X_i$, based on past observations of both $Y$ and $X_i$.
Let's assume that both Y and Xi are standardized (mean $= 0$, std $= 1$).</p>
<p>Problem is that ridge regression introduces bias into... | g66721 | [
0.04918448254466057,
-0.10410723090171814,
0.012415898032486439,
-0.046021655201911926,
0.034828752279281616,
-0.06185967102646828,
0.021868323907256126,
0.02336287684738636,
-0.034756675362586975,
0.019040396437048912,
0.030215304344892502,
0.07686156034469604,
0.025160880759358406,
0.007... |
<p>Is there a specific rule to the number of units in the treatment and control group. I am trying to carry out a difference-in-difference estimation and in the treatment group I have about 9000 individuals and in the control group I have about 800 individuals.</p> | g66722 | [
-0.04466403275728226,
0.020441880449652672,
-0.007212772499769926,
-0.03612683713436127,
0.07396562397480011,
-0.02385660633444786,
0.014827934093773365,
0.09998223930597305,
-0.0018171205883845687,
0.002596097532659769,
-0.01049196906387806,
0.03286953270435333,
0.004331967793405056,
0.00... |
<p>i am very new to this field, so please bear with me.
I have 600 parameters, on which i perform simple pairwise x,y correlations.For adjustment of the p-values ive been stuck between two R-packages.</p>
<p>FDR-tool gives me a set of qvalues, </p>
<pre><code>FDR <- fdrtool(as.vector(a$P[!is.na(a)]), statistic=c("... | g66723 | [
0.041710950434207916,
-0.05701599270105362,
-0.020020995289087296,
-0.004696750082075596,
0.04453836381435394,
-0.060818735510110855,
0.027441972866654396,
-0.01294739730656147,
-0.030428417026996613,
-0.04481662064790726,
-0.015042368322610855,
-0.017486147582530975,
0.04657115042209625,
... |
<p>I know this is a pretty vague question but I was wondering if there was a rule of thumb relation between the mean and the standard deviation of a given set of values by which you can say "Something's not right".</p>
<p>I'm thinking something like: <em>If the standard deviation is half the value of the mean --> rai... | g25871 | [
-0.015017233788967133,
0.036251429468393326,
-0.012132585048675537,
-0.035095956176519394,
0.037462811917066574,
0.007891876623034477,
-0.03778411075472832,
-0.013466856442391872,
-0.03859906643629074,
-0.03899790719151497,
0.01053440012037754,
0.007510429248213768,
0.001397918676957488,
0... |
<p>I am doing regression on a numeric dataset. This dataset is combined from 2 sources (one is from real-life data, one is from synthetic data). When I run cross-validation on this combined data, I get a correlation coefficient of 0.9. But when I train the model on the combined data, but test it only on real-life data,... | g25872 | [
0.044779036194086075,
-0.03234180063009262,
0.011621536687016487,
-0.017173677682876587,
0.020095771178603172,
0.04607584699988365,
0.04597093164920807,
0.05451282858848572,
0.005150658078491688,
-0.04025089740753174,
0.0193883515894413,
0.003131257137283683,
0.025949828326702118,
-0.01953... |
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