question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I am trying to estimate a multi-state model and am following the setup in the book by Mills (2011). The research units can go through different states a, b, c, and d. The research units can move between any of the four states in either direction. My problem is how to set up my data to do so. </p>
<p>I initially sta... | 72,976 |
<p>I have used minitab software to fit time series model and predict. For some models I got the following error message;</p>
<p>"Fitted model may be nonstationary or noninvertible. Completion of computation impossible."</p>
<p>Using another package the relevant models were fitted.</p>
<p>What is the reason for that ... | 46,436 |
<p>How do I forecast volatility using GARCH in STATA after estimating the conditional volatility?</p> | 72,977 |
<p>I am watching <a href="http://www.youtube.com/watch?v=9iOgAlZOf7k" rel="nofollow">the seminar</a> (around min 20) from CERN about Higgs' Boson discovery.</p>
<p>They quickly go on event classification talking about <em>boosting decision trees</em>. I am not really aware on what they need to classify -I guess they a... | 37,982 |
<p>I read that if you have a quadratic $f(x) = ax^2+bx+c$ and providing the leading coefficient $a < 0$, then $e^{f(x)}$ is the pdf of a normal distribution with mean $\mu = -\frac{b}{2a}$ and $\sigma^2 = -\frac{1}{2a}$.</p>
<p>Does this generalise to $e^{f(\mathbf{x})}$ defining a multivariate normal distribution ... | 35,137 |
<p>I am reading up on the EM algorithm for Gaussian Mixture Models, and there is consistent reference to the $i$th sufficient statistic. What is this, and why is it relevant to the algorithm?</p> | 72,978 |
<p>I have a data set grouped by a factor (like e.g. cyl in the built in mtcars in R). I plotted the estimated density funtions (desityplot) for each factor using the lattice package, e.g.</p>
<pre><code>library("lattice")
densityplot( ~mtcars$mpg[mtcars$cyl==4] )
densityplot( ~mtcars$mpg[mtcars$cyl==6] )
densityplot( ... | 72,979 |
<p>I am scoring my dataset using a logistic model. For getting the betas (coefficients) I used <code>proc logistic y = x1 x2 x3</code>.
To tell the model which are class variables I am using<code>class</code> statement. Now, lets say if I have a categorical variable (with name ppsc), which has 4 categories, the betas a... | 72,980 |
<p>I have a multiple regression with an interaction term and I would like to run it on two separate DVs. The two DVs are quite highly intercorrelated (but conceptually different). How can I control for that intercorrelation?</p> | 35,140 |
<p>I understand the logic of standardising raw data that is based on different scales into z scores so that they can compared, for example comparing a score of 75 out of 100 in one test versus 65 out of 120 in another test.</p>
<ul>
<li>Can I run the Spearman's correlation test on the z scores then? (i.e. forget abou... | 4 |
<p>As with my previous question, I'm looking at ways to impute missing data in a hierarchical time series data.</p>
<p>With al my other procedures, including the experimentation of imputation packages (<code>Amelia</code>, <code>HoltWinters</code> from <code>Forecast</code> and <code>MICE</code> imputation) I've only ... | 35,141 |
<p>I am wondering if there is any reasonably simple way of calculating the following problem:</p>
<p>Drawing, with replacement, $n$ balls from a bin of $N$ different colored balls, with a known probability of drawing each color of ball, what is the expected number of "unique" balls, <em>i.e.,</em> balls with no other ... | 72,981 |
<p>Is there a way to get the number of parameters of a linear model like that?</p>
<pre><code>model <- lm(Y~X1+X2)
</code></pre>
<p>I would like to get the number 3 somehow (intercept + X1 + X2). I looked for something like this in the structures that <code>lm</code>, <code>summary(model)</code> and <code>anova(mo... | 72,982 |
<p>I have a dataset with certain number of multi-attribute tuples. Each of the attribute values is a continuous random variable. I want to model each tuple (rather each attribute of the tuple) by a probability distribution function. The ultimate aim is to cluster the tuples. Can anyone suggest to me the best method to ... | 72,983 |
<p>I am looking for references about classical methods in regression clustering. </p>
<p>My problem is the following:</p>
<p>I have a cloud of points that are assumed to have been generated by inverse functions with different coefficients. So that I have a family of regression functions. I only know the form of the m... | 72,984 |
<p>The simplest form of a white noise process is where its observations are uncorrelated. We can check this by applying e.g. a portmanteau test such as Lung - Box or Box - Pierce. The series might be Gaussian white noise where the observations are uncorrelated and also normally distributed and hence independent. We can... | 46,446 |
<p>I am using Python's <a href="http://statsmodels.sourceforge.net/devel/generated/statsmodels.graphics.boxplots.beanplot.html" rel="nofollow">statsmodels</a> module to plot a <strong>violin/bean plot</strong> of some data. I get the error <em>"LinAlgError: singular matrix"</em> in the <strong>KDE</strong> calculation ... | 23,645 |
<p>I am trying to come up with the best way to predict payment amount for a collections agency. The dependent variable is only non-zero when a payment has been made. Understandably, there are an overwhelming number of zeros because most people cannot be reached or cannot pay back the debt.</p>
<p>There is also a ver... | 72,985 |
<p>Can anybody please help me convert yearly data into monthly and quarterly data?</p> | 35,147 |
<p>I am working on RNA-Seq data (on alternative splicing). Let's say I am looking at a particular type of alternative splicing event - <em>exon skipping</em>. For each intron (or junction), I look if it is <em>normally spliced</em> or if there is an <em>exon skipping</em> event happening. I have three biological replic... | 72,986 |
<p>I'm working through <em>Applied Linear Regression Models</em> (Kutner) and having a hard time figuring out this problem (it's actually problem 6.26):</p>
<blockquote>
<p>Given a First-Order Model with Two Predictors: $Y = \beta_0 + \beta_1X_1 + \beta_2X_2 + \epsilon$ , show that the coefficient of simple determ... | 37,922 |
<p>I have a time series and I want to check whether it has a unit root or not. I want to use the Dickey-Fuller test. How should I choose the regression equation from the three options: regression without constant and trend, with constant (drift) and with constant and trend? </p>
<p>Is there a procedure that I should f... | 72,987 |
<p>I'm using R's 'astsa' package and I get the following output from sarima. </p>
<p>Which AIC value would I use to compare this model (let's call it A) against others? When trying another model (B), model A's fit$AIC (858.19) is greater than model B's, but model A's AIC (12.38841) is less than model B's, so I'm not s... | 72,988 |
<p>Suppose that the quantity which we want to infer is a probability distribution. All we know is that the distribution comes from a set $E$ determined, say, by some of its moments and we have a prior $Q$. </p>
<p>The maximum entropy principle(MEP) says that the $P^{\star}\in E$ which has least relative entropy from $... | 72,989 |
<p>I've been trying to teach myself some statistics (all social science-related) using SPSS. It's all going well so far, I'm amazed at how much I'm managing to understand given how terrible I am at maths. However, there is one thing I don't fully understand.</p>
<p>Say I run a multiple OLS regression. Then SPSS will g... | 72,990 |
<p>I need to calculate the probability of $P(L,D)$, where $L$ and $D$ are not independent. I have estimated $P(L)$ and $P(D)$ with two distinct models and I also know $P(L|D)$ and $P(D|L)$. </p>
<p>As far as I can see it I have two different estimates of $P(L,D)$:</p>
<p>$P(L,D) =P(L) * P(D|L)$ </p>
<p>$P(L,D) =P(D)... | 72,991 |
<p>I need to implement the below two things: </p>
<p>Probability of negative return formula link <a href="http://www.styleadvisor.com/content/probability-negative-return" rel="nofollow">http://www.styleadvisor.com/content/probability-negative-return</a> & Probability of Target Return formula link <a href="http://w... | 35,150 |
<p>In particular I am interested in the scale estimator. Hopefully it is much better than that of IQR.</p> | 72,992 |
<p>I am trying to plot a graph which has two y-axes and one x-axis. </p>
<p>Consider three variables A,B,C. My first data set G1, has values of A and B. While getting this dataset in the script I kept C constant. In second dataset G2, I have B and C and was generated for some fixed value of A.</p>
<p>Now I am plottin... | 72,993 |
<p>When plotting within-subject data for condition A vs. condition B (significance tested through a t-test), should the error bars reflect standard error of the mean for each condition independently? Or should they be SE of the mean difference between A and B?</p>
<p>When there are more conditions for an ANOVA -- A vs... | 72,994 |
<p>I'd like to generate a random square matrix such that the rows are normalized to one and the diagonal elements are the maximum of their column. If there an efficient way to sample these matrices uniformly?</p>
<p>$2 \times 2$ matrices are straightforward to create. The first column is generated by sampling two inde... | 35,153 |
<p>everyone! I'm trying to plot pvalues of a test by categories (in this case, genetic loci). So, the x-axis contains gene names. I'm getting the plot to work, but the x-axis was very busy, so I am thinking of splitting the screen into several plots, each containing only a few loci (i.e., a few x values). When I attemp... | 35,154 |
<p>I would like to compute the area under the ROC-courve (AUC) metric for a classifier with multiple classes. Do you know (reliable) functions for Matlab that implement methods for that, like e.g. in [1]? </p>
<p>Thank you!</p>
<p>[1] Fawcett, T. (2006). An introduction to ROC analysis. Pattern recognition letters, 2... | 72,995 |
<p>I want to compare the effect of a drug (immunomodulator) on antibody levels in a group of patients $(n=18)$. Blood samples were taken pre- and post-treatment in each patient and the means of antibody levels compared for each study subject. At this point I guess that the best and simplest option is a "paired t test".... | 72,996 |
<p>Let's assume we have two means with corresponding standard errors.</p>
<pre><code>mean_1 = 3.75, se_1 = 0.64
mean_2 = 2.90, se_2 = 0.94
</code></pre>
<p>I would like to average the means and account for the standard error. I would like <code>mean_1</code> to contribute more (since the standard error is lower) to t... | 72,997 |
<p>I'm analyzing a survey data that contains the following 3 variables (questions):</p>
<ul>
<li>If the election was today who would you vote for in the following list?
(A, B, C, D, or E)?</li>
</ul>
<p>Let's imagine the respondent choose A in the previous item. Then, she is asked:</p>
<ul>
<li>What if A is not part... | 35,158 |
<p>I have a dataset containing a binary response variable and a few numeric predictor variables. I would like to use Conditional Inference Trees algorithm in R using the ctree function in party package. </p>
<p>However, the outcomes in the dataset are correlated because a single individual is contributing to more than... | 72,998 |
<p>I need to present information about the main predictors of a candidate's votes using a public opinion survey data. I have run a logistic regression using all the variables that I care about, but I can't find a good way to present this information. </p>
<p>My client doesn't care about the size of the effect only, b... | 72,999 |
<p>I have a set of data with 6 feature and an attached score for each data point within the set. </p>
<p>I have build a linear regressor for my data.</p>
<p>The thing is that the output values are pretty huge, approximately 10000 and I obtain values between 9600 and 10000. How can I measure the error of my system suc... | 35,160 |
<p>I am comparing different method of fitting Pareto distributed random numbers.
What seems very strange to me is that fitting a straight line in log-log scale has to be the worst numerical method and indeed it is, but when I superimpose the log-log histogram with that straight line they superimpose very good. The othe... | 73,000 |
<p>I am using SPSS to analyze my data. It is multinomial regression I am using. I have 14 predictor variables of which 9 are categorical and 5 continuous. The response variable is categorical with three categories. Then after pressing the appropriate buttons to reach at the multinomial regreesion the result displays bu... | 174 |
<p>I have got the following question relating to random walks. I would like to determine the moment when a random walk changes from being a simple random walk to start to drift at certain time. This sort of scenario could happen when temperatures start to rise or sea levels droppping. The idea is to detect that change ... | 35,161 |
<p>Coming from basically no time series back ground, this is likely a simple question, but what is the relationship between "being able to" use an additive decomposition of a series into seasonal, trend and remainder and a Box Cox transformation?</p>
<p>From Professor Hyndman's <a href="http://robjhyndman.com/research... | 35,162 |
<p>I have a dataset of 500 people and am trying to fit a prediction model using both quantitative and categorical variables. I have adjusted the dataset as much as possible, but still have one variable (which is important in the analysis) with 19 missing cases. What would you say is the best approach/program to use t... | 73,001 |
<p>Say you are on a beach that is composed of a mixture of different colored sands (for simplicity, black and white) and you wish to estimate how much there is of each type. You have a bucket that you can use to take samples of the sand and a technique to separate the different types and weigh them. Say also that the b... | 73,002 |
<p>I have a question to solve the following matrix problem:</p>
<p>$$E[( (X'X)^{-1}X \epsilon )^T ((X'X)^{-1}X \epsilon )]$$
into the solution
$$= \Sigma^{2} (X'X)^{-1}.$$</p>
<p>Where $\Sigma$ is the covariance matrix of $\epsilon$.</p>
<p>My question is how to solve this problem using the properties of matrix alg... | 35,168 |
<p>The anova command is </p>
<pre><code>anova score method/subject|method prediction method#prediction / prediction#subject|method infdir method#infdir / infdir#subject|method prediction#infdir method#prediction#infdir if(agegroup==0 & block==1), repeated(prediction infdir)
</code></pre>
<p>where <code>method</co... | 37,857 |
<p>I have two scenarios for time series data.
1) I have a uni-variate variable spanning across the time axis, are there any approaches or statistic to check whether this process is stable?
2) I have a multivariate variable spanning across the time axis, are there any approaches or statistics to check this multivariat... | 43,681 |
<p>Based on a <a href="http://stats.stackexchange.com/questions/124/statistical-classification-of-text/143#143">response</a> to the question "<a href="http://stats.stackexchange.com/questions/124/statistical-classification-of-text">Statistical classification of text</a>", I've decided that I want to use a <a href="http... | 46,468 |
<p>I have the following problem:</p>
<p>vector = {1,0,0,1...}, only consists of 1 or 0, and size of vector is N.</p>
<p>I am calculating proportion of 1 in such vector.</p>
<p>Say, I got prop_1 = 0.96</p>
<p>Precisely, my null hypothesis is:</p>
<p>H0: 0.96 is random</p>
<p>HA: 0.96 is not random</p>
<p>And, I w... | 35,169 |
<p>I have a dataset that I want to fit a simple linear model to, but I want to include the lag of the dependent variable as one of the regressors. Then I want to predict future values of this time series using forecasts I already have for the independent variables. The catch is: how do I incorporate the lag into my for... | 73,003 |
<p>My problem is i'm trying to figure out how many servers might be required to handle a theoretical maximal load of data requests. To do that I need to know what the maximum number of requests in a second might be.</p>
<p>I have a fairly limited set of data that 156,000 transactions occurred in one hour. This is th... | 73,004 |
<p>My research objective is that I would like to test if some sounds in languages are similar to each other in terms of duration. </p>
<p>In my situation, I have 4 languages with 5 sounds. The first three languages have all 5 sounds but only one language has 3 sounds. My items are divided into 6 vowels and all languag... | 73,005 |
<p>Q: For which data is it appropriate to use state-space modeling and Kalman filtering instead of smoothing splines and vice versa? Is there some equivalence relationship between the two? </p>
<p>I'm trying to get some high-level understanding of how these methods fit together. I browsed through Johnstone's new <a hr... | 73,006 |
<p>Let say I have this kind of data:</p>
<pre><code>1 01/1/1980
2 01/2/1999
3 03/12/2000
-1 03/6/2005
-5 07/07/2007
</code></pre>
<p>how can I calculate the Present Value (PV) to them in respect to current date, let say with 5% interest rate, in spreadsheet? <code>Current date</code> means today.</p>
<p><strong>[Upd... | 73,007 |
<p>I asked two different groups of subjects to answer a questionnaire of 2 yes/no questions. The "correct" way of answering the questionnaire was to answer yes to both questions.</p>
<p>I want to prove or disprove that group2 is answering better than group1.</p>
<p>My idea is to check if a get a "low" p-value in a Ch... | 35,175 |
<p>I have 7 balls to be randomly placed in four urns of size {5,3,2,2}, what is the probability of exactly three urns containing at least one ball?</p>
<p>(Phrased differently, twelve equally likely spots for the seven balls, but the first five is considered the first urn, next three the second urn, etc.)</p>
<p>Thro... | 73,008 |
<p>I have a simple question for you guys but I am studying for exams and I honestly forgot how this was done.</p>
<p>Here is the problem:</p>
<blockquote>
<p>"A vase contains 4 white marbles, 3 red and 2 green. You draw marbles
2 without putting the first one back after the second.</p>
<p>What are the chance... | 73,009 |
<p>Given a univariate sample $\vec X = X_1, ..., X_n$ with standard deviation 1 and a strictly monotone transformation $t: R \to R$ with the property that the standard deviation of $t(\vec X)$ is also 1 (where $t(\vec X)$ is $t$ applied to each $X_i$). If one know fits a normal distribution to $\vec X$ and $t(\vec X)$,... | 73,010 |
<p>I am scratching my head over this one...any help would be greatly appreciated.</p>
<p>I want to know if the average travel time between Guell Park and the beach in Barcelona using the bus or the metro differ and which one is faster. Since I do not know the distribution of travel time, I can't use a t-test; therefor... | 73,011 |
<p>Two players are throwing each one die. The one that has higher value, receives a number of points equal to the difference of the values on both dice. </p>
<p>How do you estimate probability for a winner to collect more than 100 points in 100 throws?</p> | 73,012 |
<pre><code>Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept) -57.6004 9.2337 -6.238 3.84e-09 ***
InMichelin 1.9931 2.6357 0.756 0.451
Food 0.2006 0.6683 0.300 0.764
Decor 2.2049 0.3930 5.610 8.76e-08 ***
Service 3.0598 0.... | 49,310 |
<p>I have applied clustering algorithms like k-mean, k-medoid and DBSCAN on my patients dataset. For each algorithm RapidMiner generated a clustered model (centroid table and graphs etc) and a clustered set (shows which examples are part of which cluster). Now I want some way that when a new patient come i want to assi... | 12,675 |
<p>I was just wandering if, given the AR process
\begin{equation}
X_t = \alpha X_{t-1} + \varepsilon_t, \quad \varepsilon_t \overset{iid}{\sim} N(0,1),
\end{equation}
the $X_t$ values are independent due to the independent white noise?</p> | 21,705 |
<p>I was implementing the max sum algorithm for a general graph (i.e., the ones with a cycle). I updated the messages as indicated in <a href="http://www.cedar.buffalo.edu/~srihari/CSE574/Chap8/Ch8-GraphicalModelInference/Ch8.3.3-Max-SumAlg.pdf" rel="nofollow">http://www.cedar.buffalo.edu/~srihari/CSE574/Chap8/Ch8-Grap... | 35,181 |
<p>I'm new to Topic Models, Classification, etc… now I'm already a while doing a project and read a lot of research papers. My dataset consists out of short messages that are human-labeled. This is what I have come up with so far:</p>
<ul>
<li>Since my data is short, I read about Latent Dirichlet Allocation (and all i... | 23,857 |
<p>I'm a mathematician self-studying statistics and struggling especially with the language. </p>
<p>In the book I'm using, there is the following problem:</p>
<p>A random variable $X$ is given as $\text{Pareto}(\alpha,60)$-distributed with $\alpha>0$. (Of course, you could take any distribution depending on one p... | 73,013 |
<p>Does the $R^2$ (or some other statistic) from a univariate linear regression tell me anything about how it would work in a logistic model? What if I normalized the data to mean zero?</p>
<p>I'm doing multiple logistic regression, and I'm wondering if I created a ton of univariate linear regressions, if I can use th... | 73,014 |
<p>I used generalized linear mixed models (with the <code>glmmADMB</code> package) to identify environmental factors related to parasite abundance in rodents. I used stepwise backward elimination to sequentially simplify the full model until only significant factors and interaction terms remained (Crawley, 2007). Howev... | 35,183 |
<p>I'm trying to interpretate some <strong>circles of correlations</strong> in the frame of a <strong>Canonical Analysis of Correlations</strong>.</p>
<p>I have been told that only points in the halo could be interpretated with those <strong>following rules</strong>:</p>
<ol>
<li>If their angle is close to $0$ they a... | 237 |
<p>I'm familiar with using <code>boot</code> in R to estimate a confidence interval for VaR. For example, I have a set of monthly returns for an asset, and I want a range on the 95% VaR.</p>
<p>Now, however, I'm given an empirical PDF, and I want to estimate the CI for VaR. I have no information on the distribution ... | 230 |
<p>To put it simply, I have the courses students have taken and scores on an exam. The students come from different course backgrounds. (Some have taken only course A some only D some A and D some A and B some B C and D etc etc)</p>
<p>What can test can I use to account for this?</p> | 24,905 |
<p>I have a binary classification task for German webpages for which I only have positive examples. That is why I use learning from positive and unlabeled examples as described <a href="http://www.cs.uic.edu/~liub/NSF/PSC-IIS-0307239.html" rel="nofollow">on this page</a>, also known as <em>partially supervised learning... | 38,499 |
<p>I have the model $Y_t = a + b*X_t + c*D_t + e_t$, where $t \in T = \{1,...,3000\}$ and $D_t$ is a binary variable equal to $0$ over $T \backslash \{20,21,...,30\}$, and equal to $1$ over $\{20,21,...,30\}$.</p>
<p>$c$ is highly significant in OLS.</p>
<p>However if I run quantile regression $Q_{Y_t}(\tau | X_t,D_t... | 38,062 |
<p>I want to derive the moving average process 1 from the Wold decomposition theorem. I don't know how to define the coefficient of MA(1), though it seems that it should be easy.</p> | 30,314 |
<p>What would be the expectation of $|x|^k$, where $x\sim\mathcal{N}(0,1)$, $k>0$ and $k$ is not an integer?</p> | 73,015 |
<p>I'm trying to apply a <em>Granger Causality test</em> to panel data. I've found enough literature to understand that topic. However, I've been unable to find and <strong>R</strong> package to carry out that analysis. I'm wondering if anybody know whether there is around any package to deal with that. Thanks!</p>
<h... | 73,016 |
<p>I have pairs (x, y) which I would like to regress (x independent, y dependent). Plotting them, I see distinct bands which can be attributed to a third variable. Unfortunately this variable cannot be directly measured.</p>
<p>Is there a good way to both fit the data to an equation and determine the value of the bi... | 73,017 |
<p>When I run this code (R 2.13.2, caret 4.98 on windows 7):</p>
<pre><code>library(caret)
data(iris)
TrainData <- iris[,1:4]
TrainClasses <- iris[,5]
rfFit <- train(TrainData, TrainClasses,
method = "rf",
tuneLength = 3,
trControl = trainControl(method = "oo... | 73,018 |
<p>I'm doing some followup to MANOVA analysis and I was wondering how in R you get eigenvalues for DFA model? There is a attribute <code>$svd</code> in the return value of <code>lda</code> function, but there is a conflicting information online regarding whether those are actually eigenvalues or not.</p>
<p>I'm readin... | 73,019 |
<p>Assume I have a set of independent, identically distributed univariate observations $x$ and two hypotheses about how $x$ was generated:</p>
<p>$H_0$: $x$ is drawn from a single Gaussian distribution with unknown mean and variance.</p>
<p>$H_A$: $x$ is drawn from a mixture of two Gaussians with unknown mean, vari... | 73,020 |
<p>I have two tables of interactions. One represents the number of times that a clownfish of a given species is found in an anemone of a given species. One represents the number of times that a clownfish of a given species is found in the same anemonae than a clownfish of another species.</p>
<pre><code>Table_anemone_... | 35,193 |
<p>Already posted on <a href="http://math.stackexchange.com/q/555274/106061">MSE</a>. Had no answer, so will post here.</p>
<p>Assume the number of calls per hour arriving at an answering service follows a Poisson process with $\lambda = 4$. </p>
<p>Question: If it is know that $8$ calls came in the first two hour... | 73,021 |
<p>I have a simple (may be stupid) question. I want to calculate Kullback–Leibler divergence on two documents. It requires probability distribution of each document.</p>
<p>I do not know how to calculate probability for each document. Any simple answer with layman example would be much appreciated. </p>
<p>Let's say ... | 35,194 |
<p>I am performing some analysis on understanding various characteristics of a certain population. To narrow down my selection (as I will be going through them manually), I am using different thresholds on certain measurable properties (which tell me how relevant someone is) to draw the following frequency graph. For i... | 35,195 |
<p>Consider a scenario where you are provided with KnownLabel Matrix and PredictedLabel matrix. I would like to measure the goodness of the PredictedLabel matrix against the KnownLabel Matrix.</p>
<p>But the challenge here is that KnownLabel Matrix have few rows only one 1 and other few rows have many 1's(those instan... | 73,022 |
<p>I have an interesting application I’d like some advice on.</p>
<p>A common task when working with stochastic systems in an engineering context is testing for regressions and improvements in performance. First, it’s important to have a confidence one is collecting enough data points to have an accurate assessment of... | 73,023 |
<p>I have made several experiments, the result graphs are below, I need to figure out what is the distribution function of the following random variables... Where do I start with statistical analysis of my experiment?</p>
<p>How to perform these analysis with spss?</p>
<p><img src="http://i.stack.imgur.com/arAJ4.png"... | 73,024 |
<p>Is it possible to use a Gaussian Process to relate multiple independent input variables (X1, X2, X3) to an output variable (Y)? </p>
<p>More specifically, I would like to produce a regression graph like the example shown below where confidence interval reduces around clusters of data (i.e. variance is high at x = 1... | 35,197 |
<p>I have 5 single factor regression models. Each has intuitive (positive) coefficients which is good. If I run multiple logistic regression one of the coefficients turns negative.</p>
<p>If I run stepwise selection, the negative coefficient stays in.. it's not redundant..</p>
<p>How should I deal with this? Is there... | 73,025 |
<p>I have a large dataset and have performed a multilevel regression in Stata, the model is the following:</p>
<p><code>xtmixed dependent independen1 independent2 independent3 independent4 || independendt5:</code></p>
<p>So there is one grouping factor: <code>independent5</code></p>
<p>In R I did the following:<... | 73,026 |
<p>I have a set of 20 chemical indicators measured in soil samples collected from one (the same) place over some time. What i would like to find out is:
- To find which indicators are somehow correlated with others. I don't want to assume dependent / independent variables, just to see if some parameters seem to be corr... | 73,027 |
<p>What does the term "Repeated" mean in the context of ANOVA? I totally understand the distinction between within-subjects test and in-between subjects test, but am not familiar with the wording "repeated" in the following context: "ANOVA:Repeated Measures - between factors" and "ANOVA: Repeated Measures - within fact... | 35,199 |
<p>Consider two random variables $X$ and $Y$ with joint distribution $F_{X,Y}$ and strictly positive density function $f_{X,Y}$. Additionally, let $x^*$ be the value of $x$ that solves:
$$
\Pr[Y<y\mid X=x^*]=1-k
$$
for some constant $k \in [0,1]$.</p>
<p>I would like to know the minimum conditions I should impose ... | 73,028 |
<p>In toxicology machine learning methods are used to estimate the probability of compound toxicity.</p>
<p>Unfortunately most toxicology datasets contain on the order of 100 compounds and sometimes contain many more variables than compounds. </p>
<p>When organizing the creation of new data one might ask how we can ... | 73,029 |
<p>I'm not well-versed in statistics at all. I'm currently working on an implementing an optimization algorithm, and am having a bit of trouble on this part.</p>
<p>I have an array of $n$ elements $A = \left\{a_{i}\right\}$ where $a_{i}\in\mathbb{R}$ and $1 \le i \le n$. Furthermore, I have an array of probabilities g... | 17,775 |
<p>A particular series (std), seems to exhibit a trend-like behavior. According to the ADF test for this series:</p>
<pre><code>Dickey-Fuller = -2.8618, Lag order = 6, p-value = 0.2131
</code></pre>
<p>Therefore, I am taking the first difference of std with this code</p>
<pre><code>stddif1<- diff(std)
</code></pr... | 73,030 |
<p>I am trying to verify a certain derivation of <strong>linear minimum mean square error estimator</strong> as it appears in [1] (also called <em>linear a posteriori estimate</em>, since the estimate is based on measurement).</p>
<p>Linear estimator is assumed $\hat{\mathbf{x}}(\mathbf{z}) = \mathbf{Az} + \mathbf{b}$... | 35,205 |
<p>I am trying to answer the following question: "How much (binary) data do I need for my learner to have seen every variable of the dataset at least once?" In my set-up I am feeding my algorithm binary vectors (i.e. with all elements equal to either 1 or 0), these vectors have a known 'density' (average amount of ones... | 35,206 |
<p>I've done a literature review. The variable <code>treat</code> takes only TRUE and FALSE values. It says whether they applied a given treatment in a given article.
I want to know if the probability of applying the treatment changes depending on the <code>journal</code> and on the <code>article.type</code>. By the wa... | 35,207 |
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