question stringlengths 37 38.8k | group_id int64 0 74.5k |
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<p>My question pertains to section 2, called "Multi-class Logistic regression", of this <a href="http://web.engr.oregonstate.edu/~xfern/classes/cs534/notes/logistic-regression-note.pdf" rel="nofollow">pdf</a>, especially the update rules. (The entire section is only a couple of paragraphs.)</p>
<p>Everything seems to ... | 73,145 |
<p>I work with 4 sequence datasets that I want to compare. The datasets range from roughly 150 to 2000 sequences. I've been able to use TraMineR on datasets up to 1000 sequences long, but when I try to run the dataset with 2000 sequences, even our University's supercomputer cannot finish in under 36h. Hence, I'm consid... | 73,146 |
<p>Good afternoon,</p>
<p>I am attempting to fit a state space model of the form:
$$
(S_t- \mu) = G*(S_{t-1} - \mu) + E_t
$$
$$
Y = F*S_t + v_t
$$
Where $Y$ is nx1, $G$ is 3x3, $S_t$ is 3x1, $\mu$ is 3x1, and $F$ is 17x3. For the life of me I cannot figure out how to define this in the DLM package in R.</p>
<p>I have... | 73,147 |
<p>I am building a churn predictor that takes a time-series as an input and returns a binary prediction that indicates whether that account will churn or not in the next two weeks. I built a training set that included two types of time-series examples - time-series of cancelled accounts 2 weeks before they cancelled (... | 73,148 |
<p>A question about equality</p>
<p>$$F_{r_{1},r_{2},\alpha}=\frac{1}{F_{r_{2},r_{1},1-\alpha}}$$</p>
<p>We know if $X\sim\chi^{2}\left( r_{1}\right) ,~Y\sim\chi^{2}\left(
r_{2}\right) $ and $X,~Y$ independent then</p>
<p>$$\frac{X/r_{1}}{Y/r_{2}}=F\implies\frac{Y/r_{2}}{X/r_{1}}=\frac{1}{F}$$
distributed. But ho... | 776 |
<p>I have done a job satisfaction survey where the DV is a 7 point Likert type scale and 5 IVs with 6 point Likert-type scale and 6 IVs with 5 point Likert type scale, all ordinal. </p>
<p>Which type of analysis is suitable for this kind of study? Between ordinal and multinomial regression which is best suited to ana... | 73,149 |
<p>Given a set of random variables $\{X_1, X_2, \dots, X_M \}$ and a (complete) dataset $D$, I have used some standard (greedy) algorithms to find good candidates to be the "true" bayesian network modeling/behind the joint probability distribution of these variables.</p>
<p>At the end, I have a set of different bayesi... | 73,150 |
<p>Is there any module for Python that computes the stationary distribution of a Markov chain, given the generator matrix?
Thanks for any help!</p> | 35,404 |
<p>What are the methods that can be used for evaluating the similarity of the sequences? Lets say that we have three sequences; I want to be able to say that "statistically" the sequence number 1 and the sequence number 3 are similar, but the sequence number 2 is "statistically" distinct. Like a p-value for statistical... | 73,151 |
<p>I have a weekly time series representing costs for a cohort. I want to tell whether an intervention on the cohort (we can assume it happened in a single week) has decreased costs for the cohort. I happen to know that the trend over this period for the population from which this cohort was taken was -120 per week per... | 73,152 |
<p>I would like to create a random forest using the following process:</p>
<ul>
<li>Build a tree on a random samples of the data and features using information gain to determine splits</li>
<li>Terminate a leaf node if it exceeds a pre-defined depth OR any split would result in a leaf count less than a pre-defined min... | 530 |
<p>I have a dataset which consists of roughly 40,000 observations grouped into 12 classes.</p>
<p>I did a quick random forest run on a single split of 80% training and 20% testing (Dont bring up the discussion on wether or not it is necessary to split data in random forests, this is just a quick experiment) and got th... | 35,406 |
<p>I have the following python dataframe (5 rows out of nearly 15,000):</p>
<pre><code> N0_YLDF MAT MAP
0 6.286333 11.669069 548.8765
1 6.317000 11.669069 548.8765
2 6.324889 11.516454 531.5035
3 6.320667 11.516454 531.5035
4 6.325556 11.516454 531.5035
</code></pre>
<p>I run OLS using f... | 73,153 |
<p>One of the most commonly misused statistical technique is scaling. Most of the time, we normalize the data with the knowledge that we don't process in the first place from training data. I recently found LIBSVM a good tool doing SV machinery. However, I am not so sure if I agree with the scaling data in the model. I... | 48,779 |
<p>Before posting this question, I searched CV for a similar question that could helped me, but I didn't find one. So, I'm sorry if this has already been asked before.</p>
<p>So, I'm self-studying from <a href="http://www.amazon.co.uk/Mathematical-Statistics-Chapman-Statistical-Science/dp/158488178X/ref=sr_1_1?s=books... | 73,154 |
<p>When designing a factor graph, the designer needs to specify the structure of the graph (encoding independence assumptions), and the form and parameterization of the energy functions for the individual factors.</p>
<p>Are there best practices for designing the energy functions?</p> | 73,155 |
<p>I am having coding the following in R
I want to pick 10 random numbers from a standard normal distribution whose sum equals 5.
I have the following code so far (below), but this returns "numeric(0)" when the random numbers don't satisfy the condition. What I want is to choose 10 random numbers that do satisfy this c... | 73,156 |
<p>Apparently, a learning algorithm must make a trade off between bias and variance when producing a hypothesis. Bias means systematic deviation from data. Variance refers to the error due to fluctuations when applying the hypothesis to different training sets.</p>
<p>Why must there be a trade off here?</p> | 73,157 |
<p>My problem is that i have created four candidate models that I am comparing mainly via the following performance measures: <code>F-measure</code>, <code>recall</code>, <code>precision</code>, <code>accuracy</code> and visual <code>ROC assessment</code>. </p>
<p>The problem is that as you see from the table, the SVM... | 35,413 |
<p>What is the effect of increasing or decreasing the number of states in markov chain process ?</p> | 73,158 |
<p>I have a non standardized t distribution with parameters $\nu$,$\beta$ (or sometimes also denoted by $\sigma^2$) and $\nu$. Now I want to get the quantiles of it. qt just calculates the quantile of a standardized t distribution, I know there exist a monotonic transformation, BUT I do not want to use this, so I want ... | 35,415 |
<p>I'm new to statistics, so I'm having some trouble interpreting some results. </p>
<p>Let's say I was interested in creating a daily wind speed profile for the arctic during a 30 day period. I have 5 different weather stations setup to measure x and y wind speed. The x and y wind speeds are independent, and both are... | 73,159 |
<p>If you've been given results for a regression analysis and asked how you would extend the analysis to find whether a new variable also affects the response variable how do you do it? Is it by considering a model with the new variable as a full model and testing whether a reduced model is adequate or is an added vari... | 35,417 |
<p>I am really confused about how to calculate precision and recall in supervised machine learning algorithm using NB classifier with more than two classes.</p>
<p>Say for example </p>
<ol>
<li>I have three classes $A$, $B$, & $C$ </li>
<li>I have $10000$ Documents out of which $2000$ goes to training sample se... | 73,160 |
<p>I've read the sampling error examples in Wikipedia, but I still don't understand. Could you give me a simple and characteristic example for sampling error?</p> | 38,127 |
<p>First of all, I realize multiple regression does not really give actually "causal" inferences about the data. Let me explain my current case:</p>
<p>I have four independent variables which I hope (but am not sure) are involved in driving the thing I'm measuring. I wanted to use multiple regression to see how much e... | 73,161 |
<p>I believe that for ANOVA unbalanced means unequal groups. But for randomised controlled trials unbalanced seems to mean something like groups of different characteristics despite randomisation. So in case of RCTs does unbalanced simply mean unlucky randomisation? Nothing to do with group sizes? What's the definition... | 73,162 |
<p>Suppose you wish to test the hypothesis that the mean of a distribution equals the median, given some samples drawn from the distribution. How would this be done? I am guessing that the test statistic would be (the absolute value of) the sample mean minus the sample median, but am not sure about the standard error o... | 35,420 |
<p>I'm trying to cluster some spatial statistics for some behavioral estimation. However, parts of the trajectory report exactly 0 speed, which implies some kind of resting state which is different from the kind of foraging state that I'm trying to extract. </p>
<p>One solution seems to remove intervals of completely ... | 35,421 |
<p>I have repeated samples of geocoordinates of activities in a city. In most of these samples positions will simply be random. In some samples, however, some percentage of the data will be arranged -- with some error -- on a line. Let me paint you a picture (code to generate this data below):</p>
<p><img src="http://... | 49,542 |
<p>I am conducting a hierarchical cluster analysis in SPSS on my database with several neuropsychological and psychiatric variables. In my database, some of my variables (that is: two pairs of variables) have intercorrelations (<em>r</em> > .80). My first thought was to eliminate these variables from my cluster analysi... | 73,163 |
<p>Currently I'm analysing around 300 items in the field of education.</p>
<p>I'm interested in the dimensionality of the dataset. So I compute a matrix of tetrachoric correlation. The goal is to do a factor analysis on this matrix.</p>
<p>By curiosity I compare to a matrix of Pearson correlation, and the results are... | 73,164 |
<p>I'm trying to remove positions that contain fixed values from strings of random data. An example is removing the string "ISBN" from a book isbn code without prior knowledge of that being a fixed string or where in the string it occurs, but with the knowledge that it won't move around. A complication is that they don... | 73,165 |
<p>The problem is to come up with a classifier for any task based on a set of attributes of an entity having different values at different times. For instance think about football players and their match stats varying from match to match (accurate shoots, passes, possessions etc.)
Then you can train a model for any tas... | 73,166 |
<p>I try to do a linear regression of a positive continuous dependent variable (outcome) with several independent variables (all of them are categorical / binary). I had many troubles to get Gaussian residuals (the distribution of my outcome variable is not Gaussian itself).</p>
<p>I tried a lot of transformations for... | 73,167 |
<p>I have two rather conceptual questions about random forest classifiers. Before we get there, I quickly want to lay out the problem I am working on: I have large a large data set consisting of 300 samples with about 370,000 data points each. There are 6 different groups of 50 samples each. I constructed a RF classifi... | 73,168 |
<p>I am trying to follow along in the Statistical Sleuth <a href="http://www3.amherst.edu/~nhorton/sleuth/" rel="nofollow">here</a> to teach myself some regression analysis for my job in machine learning, but when installing the "mosaic" package it requires the "car" package. So I did <code>install.packages(car)</code>... | 25,214 |
<p>I'm using SPSS and this drop-down menu: <code>Analyze -> General Linear Model -> Univariate.</code> </p>
<pre><code>DV: Number of times patient visited doctor over one year
Factor 1: 2 levels: Two different drugs
Factor 2: 2 levels: Gender
Factor 3: 4 levels: Race
Factor 4: 3 levels: drug tak... | 73,169 |
<p>I write this question with reference to an example on p138-142 of the following document: <a href="ftp://ftp.software.ibm.com/software/analytics/spss/documentation/amos/20.0/en/Manuals/IBM_SPSS_Amos_User_Guide.pdf" rel="nofollow">ftp://ftp.software.ibm.com/software/analytics/spss/documentation/amos/20.0/en/Manuals/I... | 73,170 |
<p>I am currently trying to implement some Machine Learning algorithms on my own. Many of them have the nasty property of being hard to debug, some bugs don't cause the program to crash, but rather work not as intended and seem as the algorithms just gives weaker results.</p>
<p>I would like to have some way of increa... | 73,171 |
<p>From what I have come to understand, the events A and B are considered independent for purposes of probability theory when</p>
<p>$$
p(A \cap B) = p(A) \cdot p(B)
$$</p>
<p>Now, supposing I flip two coins. I write down the probabilities for the joint outcomes as $\left(\frac{1}{4}, \frac{1}{4}, \frac{1}{4}, \frac{... | 12,720 |
<p>I am new to statistics and SPSS. I have a questionerre having 30 likert scaled questions, and 5 factors each having 5 or 6 questions. I made the reliability analysis and no problem is found. all factors have alpha greater than 0.7. Now I want to make the correlation analysis between factors to validate my hypothesis... | 22,996 |
<p>I need to create a computer program for randomizing subjects using <a href="http://books.google.com/books?id=pIx-0LvD6agC&pg=PA103&lpg=PA103&dq=%22stratified%20randomization%22%20sample&source=bl&ots=LeKceTQLbR&sig=u2diN1kzLbYSSu56ZqwMOZkNDN0&hl=en&sa=X&ei=nnMAUbrINIuzigKaxIGABg&a... | 73,172 |
<p>I am running an Cox regression with my data. In my final model I had four potential predictors and did first a forward (Wald method) Cox regression and then for validation of my model a backward (Wald method) cox regression. Unfortunately I got two different models. What can I do now? Is there any convention to deci... | 73,173 |
<p>who can help me to resolution of this statistic exercise? below the track: Caio go in a bank,the number of customers ahead him are described by a Poisson random variable of parameter a>0. Calculate the average waiting time knowing that: -the waiting time is given by the sum of service time of single person. -the tim... | 73,174 |
<p><img src="http://i62.tinypic.com/2exy4up.png" alt="Neural network image"></p>
<p>I am sure this is a pretty easy question for someone well versed with neural networks but it has had me running round the bends.</p>
<p>While I understand how this is to be done in principle, i.e. readjustment of weights according to ... | 73,175 |
<p>I'd like to plot the probability distribution for a set of binomial trials in R, the catch is that each trial has an independent probability of success (which I have in vector form).</p>
<p>So, in R if I were doing this with coin tosses: <code>plot(x,dbinom(x,10,.5))</code> would work, where <code>x</code> is <code... | 49,915 |
<p>I would like to regress basal metabolic rate (BMR) on height, weight, age and gender. How do I do this taking into consideration the interaction between the variable? Wouldn't I have to consider interactions upto fouth order?</p> | 23,087 |
<p>I’m trying to model a time series (log_consommation) in a ARIMA(p,d,q) using <code>Stata</code>.</p>
<p>So I start by determining d by transforming my time series to make it stationary.</p>
<p>My question is, when performing an augmented Dickey Fuller test to test stationarity, I have to choose the number of lags.... | 35,433 |
<p>A document I read many years ago (to do with actuarial education; sorry I can't link to a copy) used chi-square tests to assess lack of fit of various models to mortality rates which were treated either as (scaled) binomial or Poisson, or as normal.</p>
<p>It advocated a blanket rule of thumb for dealing with model... | 73,176 |
<p>I am a doctoral candidate and for my dissertation research I am using two standardized scales as independent variables. Because these have not been used with my particular population, I needed to do some validation. Both produced good alphas, but both failed when it came to the CFA. I've been told that I can just ... | 73,177 |
<p>I've been trying to figure out a way to perform LASSO with L1 loss function (instead of the L2 loss) but have been completely dumfounded as to how. </p>
<p>I've attempted to use the flare package's flare.slim() function but receive the error </p>
<pre><code>Sparse Linear Regression with L1 Regularization.
Error in... | 35,436 |
<p>Assume that each person can only have one of three eye colors: blue, brown or green. Furthermore assume that I have two vectors that describe for N individuals the (simulated) probability that the individual has eye color blue (p1) and eye color brown (p2).</p>
<p>How can I assign a unique eye color to each of the ... | 73,178 |
<p>My mother heard about free SPSS 16 and gave me the task of finding a safe download of it. However, I can't find <em>any</em> site (except torrents) that actually have it available, they all seem to use SPSS 16 as a bait and switch to take you to the page with the latest version.</p> | 73,179 |
<p>I noticed that if $X$ is a RV in $[0,1]$ then $V[X] \leq E[X](1-E[X])$, which also implies that the bernoulli distribution maximizes variance (one of many solutions). </p>
<p>For interest's sake consider the discrete case: let $p_i \geq 0$ give probability of $1 \geq x_i \geq 0$, we assume: $V[X] > E[X](1-E[X])$... | 73,180 |
<p>$IQ = b_0 + b_1Group + b_2Age + b_3Income + b4\times Group\times Age$</p>
<p>Group is dummy coded ($0,1$)</p>
<p>I assume that the interaction of Group x Age tests the group difference in the slope of the IQ vs. Age regression line while controlling for Income. </p>
<p>I would like to show a scatter plot of the... | 46,789 |
<p>I have three data sets like this:</p>
<p>data1: {A, A, B, C, D, ..}
data2: {A, B, B, C, E, ...}
data3: {A, C, D, D, E, ...}</p>
<p>How do I test if these three data sets are from the same distribution?</p> | 48,037 |
<p>If $X$ is a categorical variable, and I am interested in the posterior distributions of $\beta_1$, where $\beta_1$ is a vector of coefficients, one for each level of X, are these equivalent models?</p>
<p>Model 1:
$$Y \sim ( \beta_0 + \beta_1X_1,\sigma^2)$$
$$\beta_1 \sim N(0,\tau)$$</p>
<p>Model 2:
$$Y \sim(\beta... | 35,440 |
<p>I have a question about loss function in bayes classification. Let see similar case of loss function in linear classification:
Given data $(x,y)=${$(x_1,y1)....(x_n,y_n)$} is map to label $T=${-1,1}. The loss function of that method is given by
$$L=\sum(y-T)^2$$
How about if I use bayes classification,which is loss ... | 73,181 |
<p>As the title says, I'm getting some interesting results from gbm.perf. The first time I ran into trouble was after a run where n.trees was set to 7,000. When gbm.perf also returned 7,000 I got suspicious. So I ran a test where n.trees was 7. gbm.perf's value: 7.</p> | 35,442 |
<p>I am looking at trigger efficiencies, meaning that I have some device that fires on $k$ out of $n$ events. In the end I am interested in some estimate of the efficiency $\epsilon$ which is the probability to fire on a randomly given event. Using a Bayesian approach with a uniform prior over $[0,1]$ I can model the p... | 35,443 |
<p>I am trying to use the R package urca. It has functions cajorls and carools, which do OLS regression of restricted and unrestricted VECM respectively. Both functions take in the VECM estimated using Johansen test and return the regression parameters and cointegrating vectors.</p>
<p>I do not understand why is there... | 73,182 |
<p>The response was calculated as $\frac{Control-Observation}{Control}*100\%$. Raw values of $Control$ and $Observation$ are not available, I have only calculated values. Each value was measured twice. The scatterplot of two measurements is presented at the figure
<img src="http://i.stack.imgur.com/JYehn.png" alt="Two ... | 73,183 |
<p>I try to understand how to forecast with the rugarch package, espcially the command <a href="http://www.inside-r.org/packages/cran/rugarch/docs/ugarchforecast" rel="nofollow">ugarchforecast</a>.
I have problems with understanding the n.roll and the out.sample command.</p>
<p>The n.ahed command is clear to me. It sa... | 46,792 |
<p>Consider the data below. (Dependent Variable: Human Development Index (HDI))</p>
<pre><code> Coefficient Std. Error t-ratio p-value
const -0.260523 0.129316 2.0146 0.05693 *
LITRATE 0.0031374 0.000965695 3.2488 0.00384 ***
LIFEXP 0.0051052 0.00268771 1... | 35,444 |
<p><strong>Why Hierarchical? :</strong> I've tried researching this problem, and from what I understand, this is a "hierarchical" problem, because you are making observations about observations from a population, rather than making direct observations from that population.
Reference: <a href="http://www.econ.umn.edu/~... | 73,184 |
<p>So, the idea of a two sample t-test is pretty simple. Two samples, each with values drawn from a given set. Consider the difference in the means of the two sample - the mean and variance of its distribution. Then, calculate the t-statistic and finally the p-value on the assumption that the difference follows a t-dis... | 73,185 |
<p>I am fairly new to R and data mining concepts and am trying to understand the rpart package in R. I am a bit confused about the role of priors and loss in the making of a decision tree. I am referring to the <a href="http://cran.r-project.org/web/packages/rpart/vignettes/longintro.pdf" rel="nofollow">http://cran.r-p... | 73,186 |
<p>I've recently embarked on fitting regression mixed models in the Bayesian framework, using a MCMC algorithm (function MCMCglmm in R actually).</p>
<p>I believe I have understood how to diagnose convergence of the estimation process (trace, geweke plot, autocorrelation, posterior distribution...).</p>
<p>One of the... | 46,801 |
<p>I have 100 variables , each variable has a set of values between {0,100} .
My null hypotheses is : For all variables, the maximum value of the values set is not greater than 10 </p>
<p>How to test this null hypotheses statistically ?</p> | 73,187 |
<p>Suppose we have $N$ independent random variables $X_1$, $\ldots$, $X_n$ with finite means $\mu_1 \leq \ldots \leq \mu_N$ and variances $\sigma_1^2$, $\ldots$, $\sigma_N^2$. I am looking for distribution-free bounds on the probability that any $X_i \neq X_N$ is larger than all other $X_j$, $j \neq i$. In other words,... | 73,188 |
<p>Method "A" describes biological samples using multivariate "fingerprints" that consist of about 30 different variables. Different variables show different typical distribution and many of them closely correlate one with another. From prior experience it is assumed that we cannot transform many of the variables to n... | 73,189 |
<p>I am testing six groups on six different websites that fall under two categories (responsive websites and mobile websites). Each group contains 10 participants. One group rate one site in one category. No overlapping. The groups were tested using a Usability scale (1-10). What is a suitable statistical approach to i... | 35,451 |
<p>I've seen two forms for the estimated coefficients, wondering what the difference is (if there's any), or if I'm missing something:</p>
<p>from regression models book
$$b = (X'X)^{-1}(X'X)Y$$</p>
<p>from wikipedia and my lecturer
$$b = (X'X)^{-1}(X')Y$$</p> | 73,190 |
<p>I was working through <a href="http://cran.r-project.org/web/packages/HMM/index.html" rel="nofollow">HMM</a> R package and used posterior as well as Viterbi algorithm:</p>
<pre><code>R> hmm = initHMM(c("A","B"), c("L","R"), transProbs=matrix(c(.8,.2,.2,.8),2),
+ emissionProbs=matrix(c(.6,.4,.4,.6),2))
R&g... | 35,452 |
<p>I performed an experiment where I raised different families coming from two different source populations, where each family was split up into a different treatments. After the experiment I measured several traits on each individual.
To test for an effect of either treatment or source as well as their interaction, I... | 46,806 |
<p>I am running an analysis looking at individual voter turnout where it is a 1 for voting and 0 for not voting. I have some information on individuals including age, gender, and several years of past voting history. I can also geocode the information and add all sort of other grouped or clustered data including scho... | 35,453 |
<p>The following code</p>
<pre><code>PredictNew <- predict (glm.fit, newdata = Predict, X1 =X1, Y1= Y1,
type = "response", se.fit = TRUE)
</code></pre>
<p>produces a 3-column <code>data.frame</code>--PredictNew, the fitted values, the standard errors and a residual scale term.</p>
<p>Perfe... | 73,191 |
<p>I was curious if there was any bounds or approaches to getting good estimates for a probability from the following generating process.</p>
<p>Suppose we have 2 sets of objects $A$ and $B$ where both sets are large and possibly infinite. The generating process is that $a \in A$ is drawn from a categorical distributi... | 35,454 |
<p>Can someone explain or point me to an introductory reference that deals with the notion of sparsity in Bayesian modeling? What does the idea of sparsity really mean? What does it mean to 'induce sparsity'? How are 'sparse priors' identified and used? In fact, what are they? </p> | 73,192 |
<p>I'm hoping somebody can help me out with this question.
For a study I did a path analysis, which looks like this:</p>
<pre><code>IV -->
Mediatior --> DV
IV -->
</code></pre>
<p>So I have two IV's leading to my mediator. With SPSS I did two regression analysisses from the IV's to the Mediator. </... | 73,193 |
<p>My friend collects stickers. There are 200 unique stickers to be sticked into the album. As the album gets fuller, it gets less and less likely that any newly obtained sticker is not already in the album.</p>
<p>I assumed every sticker to be obtained equally likely and figured the expected number of stickers necess... | 73,194 |
<p>I'm fitting a mixed multilevel model in R using the <a href="http://cran.r-project.org/web/packages/nlme/index.html" rel="nofollow">nlme</a> package, and I don't understand what is the difference between the covariance structures <code>corAR1</code> and <code>corCAR1</code>. Can someone help me?</p> | 46,809 |
<p>Stata has the very useful function <code>ivprobit</code>. For example:</p>
<pre><code>use http://www.stata-press.com/data/r11/laborsup.dta
ivprobit fem_work fem_educ kids (other_inc = male_educ)
</code></pre>
<p>Is there a package for doing this in R?</p> | 73,195 |
<p>I'm confused about the calculation in the below problem. We're given Var(X) and Var(e) but where does the 2^2 term come from (or is that a Z^2?)? What formula for calculating variance is being used here?</p>
<p><img src="http://i.stack.imgur.com/DkRBi.png" alt="enter image description here"></p> | 73,196 |
<p>Edited to restrict one of the gamma distributions to be an exponential distribution, and to force both means to 1.0, and to add wolfram alpha links:</p>
<p>I have two distributions, both with mean 1, and I want to compare their cdfs when $0 \lt x \lt 1$. One of the distributions is exponential, and the other distr... | 35,459 |
<p>I have a multivariate dataset that changes over time. I have extracted (and normalised) some features and used k-means to generate clusters over the entire span of the dataset.</p>
<p>Now I want to see whether the clusters change significantly over time. So working backwards, and thus reducing the dataset by x-mont... | 73,197 |
<p>I am using <code>fourier()</code> function of R which has arguments x,h,K. Can any body please explain me what is 'K' in this function and what is the use of it.</p>
<p>Thanks in advance.</p> | 73,198 |
<p>I am using the bootstrap approach for internal validation of a multivariate model built with either standard logistic regression OR elastic net. </p>
<p>The procedure I use is as follows:</p>
<p>1) build model using the entire dataset, obtain predicted values, and calculate AUC (AUC_ap, apparent)</p>
<p>2) genera... | 35,462 |
<ol>
<li><p>I ran a GBM model in R with loss function as bernoulli and n.trees=1000. I want to see the weights assigned to the predictions coming from 1000 trees. Is there any command in R that does that?</p></li>
<li><p>How does GBM split nodes while constructing trees? How does it determine the first variable to spli... | 73,199 |
<p>A fair coin is tossed until a head comes up for the first time. The probability of this happening on an odd number toss is? How do I approach this problem?</p> | 73,200 |
<p>I am reading the regression analysis resutls in a paper which showed most of the coefficients b2 and b3 are not significant but the R2 is significant. Eventhough there aren't too many variable in this model(see the model below), that happend. How come? </p>
<p>Is it still necessary to watch b2 and b3 and make concl... | 49,368 |
<p>I am conducting some experiments on a data set that was collected by convenience. It is a data set based on historical data, most of which is not digitized. I know the exact distribution of the historical data but do not have the data itself. Instead I have an incomplete subset. Looking at the distribution of this s... | 73,201 |
<p>I understand that <a href="http://en.wikipedia.org/wiki/Multinomial_test" rel="nofollow">multinomial tests</a> and <a href="http://en.wikipedia.org/wiki/Binomial_test" rel="nofollow">binomial tests</a> are both likelihood ratio tests for testing if a sample has a categorical or Bernoulli distribution.
<a href="http... | 73,202 |
<p>Given a single finite population of size N, if I obtain S random samples from the data (replacing after each one), and randomly partition these into 2 sets of S/2 random samples, can I treat these two sample distributions as statistically independent? </p>
<p>If, somehow, I am able to identify duplicates, are the t... | 404 |
<p>I am working with a model that can be described roughly as </p>
<p>$$
\left\{ \begin{array}{ll} y^* & = & \beta_0 + x'\beta + \epsilon_{\{x,v\} }
\\ w^* & = & \gamma_0 + v'\gamma + \delta_{\{x,v\} }
\\ y & = & 1[y^* >0 ]
\\ w & = & 1[w^* >0 ]
\end{array} \right.
$$
although ... | 73,203 |
<p>Does anybody know why it is not possible to compute standardized residuals when estimating a Tobit model?</p>
<p>Here is a short example of what I am talking about:</p>
<pre><code>> require(AER) # for tobit estimation commands
> require(MASS) # for computing standardized residuals
> numberofdrugs <-... | 45,148 |
<p>I have a feeling this may have been asked elsewhere, but not really with the type of basic description I need. I know non-parametric relies on the median instead of the mean to compare... something. I also believe it relies on "degrees of freedom"(?) instead of standard deviation. Correct me if I'm wrong, though.... | 49,450 |
<p>I have been hearing this frequently that gaussian processes is a smoothing operation. I didn't get what they mean by that. Any clarifications guys?</p> | 73,204 |
<p>I am building a small application to calculate clusters from some input set (a n x p matrix). After I finish running the algorithm to get k clusters I also obtain the centroid of each cluster (a k x p matrix).</p>
<p>Then I need to plot the results, so I run Principal Components Analysis to map the input set into 2... | 73,205 |
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