question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I know how to test for heteroskedasticity using pooled OLS?</p>
<p>But how can I do it after I have run a Random Effects model?</p>
<p>If I find heteroskedasticity in pooled ols does it mean it is also present in the RE model?</p> | 17,871 |
<p>I have read that Kendall W should be avoided when it comes to deal with non-rankings <a href="https://www.ibm.com/developerworks/community/forums/html/topic?id=77777777-0000-0000-0000-000014903859" rel="nofollow">especially for rating scales which tend to have a lot of ties</a>.
Yet <a href="http://stats.stackexchan... | 73,031 |
<p>I'm having difficulties understanding what type of statistical testing I need for my questions. My measurements include the following: </p>
<pre><code>Organism 1 Location 1 5 repeated measurements
Organism 1 Location 2 5 repeated measurements
Organism 1 Location 3 5 repeated measuremen... | 17,887 |
<p>It is for my master thesis, I need to go more in depth.
Any suggestion about recent works is really welcome.</p> | 73,032 |
<p>I have some process that succeeds or fails with probability $p$.
I can do distinct simulations to estimate $p$:</p>
<ol>
<li>Run $N$ simulations of a single process, record $N$ samples of a $\text{Bernoulli}(p)$, do GLM with binomial family to estimate $\log(p/(1-p))$.</li>
<li>Run $N$ simulations in which I contin... | 73,033 |
<p>I have to find a 95% C.I. on the median and other percentiles. I don't know how to approach this. I mainly use R as a programming tool.</p> | 35,213 |
<p>I am working with a time series of meteorological data and want to extract just the summer months. The data frame looks like this:</p>
<pre><code>FECHA;H_SOLAR;DIR_M;DIR_S;VEL_M;VEL_S;VEL_X;U;V;TEMP_M;HR;BAT;PRECIP;RAD;UVA;UVB;FOG;GRID;
00/01/01;23:50:00;203.5;6.6;2.0;0.5;-99.9;-99.9;-99.9;6.0;-99.9;9.0;-99.9;-99.9... | 73,034 |
<p>This feels like it should be a very straightforward stats analysis but I'm struggling to find a solution.</p>
<p>I have a data set made up of pre- and post-test continuous data values taken from multiple groups i.e.:</p>
<p>Group 1 (pre-test, post-test)</p>
<p>Group 2 (pre-test, post-test)</p>
<p>Group 3 (pre-te... | 44,020 |
<p><strong>Summary:</strong> when using a 10-fold cross-validation procedure where each training set is used to generate N bootstrap samples for processing with NNs. How do I provide my NN with correct sequence and elements of my response variables series to match the length of my input time series so that I follow... | 73,035 |
<p>It occurred to me that how one writes an interaction term in BUGS depends on the types of predictors that are "interacting". Suppose data that are long (rather than wide). Then, a model with an interaction between two factors, A and B, as in two-way ANOVA, may look something like</p>
<pre><code>y[i] ~ dnorm(mu[i], ... | 73,036 |
<p>I implemented ISOMAP and I plan to use it as a feature extraction technique for a classification task.</p>
<p>My problem is that although I can map the training data into a lower dimensional space, how can I use the same mapping for a separate test dataset?</p> | 35,214 |
<p>I have a health outcome (measured as a rate of cases per 10,000 people in an administrative zone) that I'd like to associate with 15 independent variables (social, economic, and environmental measures of those same administrative zones) through some kind of model (I'm thinking a Poisson GLM or negative binomial if t... | 73,037 |
<p>I have a simple statistical question (forgive me if I use statistical terminology in a wrong way)
Suppose I have a random vector with two components, $(x_1, x_2)$, where $x_1$ can take values from $1$ to $n$ and $x_2$ can take values from $1$ to $m$
and I have a two-dimensional distribution $P$ as a $n \times m$ ma... | 73,038 |
<p>I am not very new to R as I use it for my daily data analysis needs. I have been searching for an R package that can compute Standard Normal Homogeneity Test, Buishand range test, Von Neumann ratio test and the Pettitt test for daily precipitation series. The aim is to capture breaks in years where there is inhomoge... | 73,039 |
<p>I'm analyzing data from a classical intervention design. Subjects were divided into groups, undertaking different interventions. Each subject was measured using the same tests before and after the intervention. As always, the very reason to have multiple groups is that we want to isolate the effect(s) of interest. F... | 73,040 |
<p>I am trying to understand the hyperplane of the SVM algorithm. My problem is that different sources state different equations. </p>
<p>Which equation is the right one and if both are right, why?</p>
<ul>
<li><p><a href="http://en.wikipedia.org/wiki/Support_vector_machine" rel="nofollow">Wikipedia</a>: $w\cdot x... | 46,526 |
<p><strong>Question</strong><br>
Is there such concept in econometrics/statistics as a derivative of parameter $\hat{b_{p}}$ in a linear model with respect to some observation $X_{ij}$?<br>
By derivative I mean $\frac{\partial \hat{b_{p}}}{\partial X_{ij}}$ - how would change parameter $\hat{b_{p}}$ if we changed $X_{i... | 73,041 |
<p>We asked a group of subjects to tell us their preferences for a given procedure, of which there were 4 choices. We then provided them with educational material and asked them again of their preference. </p>
<p>I would like to compare the two groups and see if there is a statistically significant difference betwee... | 73,042 |
<p>If there some occlusion on face (such as sunglasses, mask, scarf), the recognition rate will decrease steeply? How to handle this case?</p>
<p>I have do a survey, the PCA reconstruction method have been mentioned by some literature. I don't know whether or not this method is the state-of-the-art method. Is there ot... | 73,043 |
<p>For some reason my supervisor wants me to centre only the independent variables that are used in interaction terms. I have never heard of such a practice. Does it make sense to partially centre data matrix $X$, that is, centering only some of the columns of data matrix $X$, not all of them?</p>
<p>Thank you.</p> | 35,218 |
<p>I posted my original question here, but was told that I should have posted at Cross Validated, below is the link to the original question:</p>
<p><a href="http://stackoverflow.com/questions/20943584/predict-binary-outcome-with-r?noredirect=1#comment31453858_20943584">http://stackoverflow.com/questions/20943584/pred... | 73,044 |
<p>I'm using the <code>glmnet</code> package in R for a relatively large dataset (~50k observations, ~1000 predictors). I'm observing weird timing behavior for different values of the <code>n_lambda</code> parameter. Using <code>cv.glmnet</code> (5-fold CV done in parallel), smaller values of <code>n_lambda</code> corr... | 73,045 |
<p>I have a 2x3x4 repeated measured anova. I have a significant 3-way interaction, and I want to make sure that I am using the correct post hoc comparisons and not violating any key statistics theory.</p>
<p>I have run the statistics in SPSS and have adjusted for multiple comparisons using SIDAK but I want to make sur... | 73,046 |
<p>For those of you familiar with <a href="http://en.wikipedia.org/wiki/Exploratory_factor_analysis" rel="nofollow">Exploratory Factor Analysis</a> (EFA) and <a href="http://en.wikipedia.org/wiki/Random_forest" rel="nofollow">Random Forest</a> (RF), I have recently had an idea of combining these two methods to reduce t... | 73,047 |
<p>I am trying to cluster a bunch of executable files, and I want to use NCD ( normalized compression distance) as the distance metric.
Is there any software package which lets me do that?</p>
<p>Update:
I'm using a python script which produces a distance matrix for example for 4 instances like:</p>
<pre><code>[[1.00... | 37,084 |
<p>For an archaeology project, I have two assemblages of items, each measured in a variety of ways (mass, area, thickness, etc.).</p>
<p>I want to test if the differences between the assemblages are significant. </p>
<p>I am pretty sure I have to use the T-Test, but I am not sure how to apply it, taking into account ... | 35,223 |
<p>I'm trying to use the sobol2007 model in the R sensitivity package. I'm doing runs on a model with 26 parameters, and using 2 sets of 500 monte-carlo samples to seed the analysis, and nboot=500. This results in 14k runs</p>
<p>When I generate the sensitivity results, I'm expecting numbers in 0..1, but I get both
* ... | 35,225 |
<p>I'm using exponential smoothing (Brown's method) for forecasting. The forecast can be calculated for one or more steps (time intervals). Is there any way to calculate confidence intervals for such prognosis (ex-ante)?</p> | 35,226 |
<p>My company gathers all sorts of series for page views, unique visitors and many other user data (collected by our web servers). As I see it, these sets of series are discrete since they are all collected by computer systems and software and there is no 'intermediate' value between the collected numbers. Also because... | 73,048 |
<p>I am looking for a reference to an elementary (or at least fairly simple) treatment of the Weibull-distribution. I have a bright high school student doing a project on wind mills and it turns out that wind speeds follow a Weibull distribution. Ideally I am looking for a derivation of the mean and standard deviations... | 35,227 |
<p>1) Let $\{a_i\}_{i = 1, ...,n}$ be a real sequence generated by a pseudorandom number generator. How can I check the randomness of such real numbers using, for instance, Runs test?</p>
<p>2) Assume three independent sequences of real numbers $\{a_i\}_{i = 1, ...,n}$, $\{b_i\}_{i = 1, ...,n}$ and $\{c_i\}_{i = 1, ..... | 73,049 |
<p>I'm new with AB testing and i want to do this with R (free and easy to learn software).</p>
<p>Can anyone help with sample code in R for AB testing?</p>
<p>Thanks
Ariel</p> | 73,050 |
<p>By using the exponential class factorization theorem, I came up with $Y = \sum (x_i)^2$ to be the complete and sufficient statistics for $\sigma^2$ .</p>
<p>Using this sufficient statistic as a condition, would I need to get the MLE to derive the MVUE for $\sigma^2$ ? </p>
<p>I don't know how to proceed to get the... | 73,051 |
<p>I proposed a question early on infection rate data in 6 different hospitals for two years (N=12). After speaking with several people I decided that a Wilcoxon-Mann-Whitney (Mann-Whitney U, Wilcoxon rank-sum) test is the best bet. What I am concerned about is whether I can use rates and what exactly the output means ... | 35,232 |
<p>The idea here is that you have a 5 vs. 5 game where each player is using a unique character (henceforth 'hero'), and thousands of matches of this game have been played. The goal of the analysis is to look for the best 2-hero combinations- those that perform better than their expected value. </p>
<p>Some heroes work... | 73,052 |
<p>On page 232 of "An R companion to applied regression" Fox and Weisberg note </p>
<blockquote>
<p>Only the Gaussian family has constant variance, and in all other GLMs the conditional variance of y at $\bf{x}$ depends on $\mu(x)$</p>
</blockquote>
<p>Earlier, they note that the conditional variance of the Poisso... | 73,053 |
<p>In Stata, I have panel data for the years 2008-2012, across 7 firms. I assign a value corresponding to <code>id</code> for all firms. </p>
<p>(<code>id</code> 1,3 are specialized firms, which is of interest)</p>
<p>I have two dummy variables. </p>
<p>One is an indicator for the 2008 global financial crisis and ... | 247 |
<p>I am using a panel of 2249 schools with data from 2002-2008. Some of the schools are single sex schools whilst others are mixed sex.</p>
<p>Some background on my regression:</p>
<p>Consider the determinants of school performance (as measured by the <strong>percentage</strong> of pupils in the school who get 5 A*-C... | 73,054 |
<p>I was reading around the Information Theoretic-AIC approach of model selection where AIC values are used to select the candidate set of models. I am quite clear on this. My question is this:</p>
<p>for mixed effects model, how to calculate the AIC values. For e.g. I have several random intercept and fixed slope mod... | 73,055 |
<p>Suppose I have the following dataframe:</p>
<pre><code>id time sale_yn number journey_nr "nVariables with observation specific variables"
abc 10 0 1 1
abc 11 0 2 1
abc 12 1 3 1
abc 13 0 1 2
def 10 0 1 3
def 15 ... | 35,236 |
<p>I am using <a href="http://www.biomedcentral.com/1756-0500/2/105" rel="nofollow">synergy factors</a> to test synergy between two variables. The equation is simple enough, where $OR_{12}$ is the combined odds ratio for variables 1 and 2: </p>
<p>$ SF = \dfrac{OR_{12}}{(OR_1 \times OR_2)}$</p>
<p>How do I calculate ... | 40,019 |
<p>I am trying to solve this problem on and off for the past couple of months but to no success. This was supposed to be a very small part of my PhD thesis in navigation but I guess I underestimated the problem. It sounded trivial at the beginning, but now I am not so sure.</p>
<p>Lets say we have two ships, each with... | 35,237 |
<p>Apologies in advance for incorrect use of terminology - I do not have much of a background in statistics.</p>
<p>Suppose I have the following behavior for daily stock returns: </p>
<p>When $r_{i+1} > r_i$, then $r_{i+2} < r_{i+1}$ with probability $>50$%. Conversely, when $r_{i+1} < r_i$, then $r_{i+2}... | 40,172 |
<p>See the related, but old question: <a href="http://stats.stackexchange.com/questions/2819/correcting-p-values-for-multiple-tests-where-tests-are-correlated-genetics">Correcting p values for multiple tests where tests are correlated (genetics)</a>.</p>
<p>Multiple comparison methods based on bootstrap have the advan... | 73,056 |
<p>I currently have log files all off different sizes, and I am trying to calculate the total probability of an event that occurs being an error. </p>
<p>For example:</p>
<blockquote>
<p>Log file #1: Has a total of 1000 entries and 20 of them entries are errors so the conditional probability for that file would be ... | 46,557 |
<p>Bacterial grow rates were measured in 4 flasks, 3 had been inoculated with different antibiotics, 1 flask was kept as a control. Measurements were taken every 20 minutes for 3 hours. The experiment was repeated 6 times.</p>
<p>I understand two way ANOVA would be inappropriate because it treats each time point as in... | 73,057 |
<p>According to <a href="http://en.wikipedia.org/wiki/Wilks%27_lambda_distribution" rel="nofollow">Wikipedia</a>, Wilks' Lambda distribution generalizes Hotelling's distribution. I am having some problems seeing how this works. I can see how Hotelling's distribution generalizes Student's t-distribution (a RV distribute... | 35,239 |
<p>I refer here to a classical linear regression whose true representation is given by the equation: $y_i=x_i'\beta+u_i$,</p>
<p>where as usual $x_i$ is a $K\times 1$ vector of independent explanatory variables, $\beta$ is a $K\times 1$ vector of parameters and $u_i$ the error term of the ith observation and by const... | 73,058 |
<p>I'm hoping someone can give me some guidance on implementing
Gaussian processes (GP) with PYMC. In particular, I'm not sure how to use
multiple GP submodels properly within a single pymc model.</p>
<p>More specifically, what I'd like to implement is a classifier for which the
input is a time-varying signal (an aud... | 35,242 |
<p>I have 63 rows and 17 columns in the cocomo81 dataset (see the information <a href="http://en.wikipedia.org/wiki/COCOMO" rel="nofollow">here</a>). The first 16 columns are the inputs to the network and the 17th column is the estimated outputs. </p>
<p>I took 2/3rd of the data for training and validation (i.e 42 row... | 35,246 |
<p>I want to build a content based recommender in a restricted environment regarding cpu power and memory (to be specific: a mobile device, but it is not acceptable to build the recommender on a remote server).</p>
<p>Which algorithm or heuristic is feasible in such a situation ? </p> | 73,059 |
<p>I have a question regarding parameter interpretation for a GLM with a gamma distributed dependent variable. This is what R returns for my GLM with a log-link:</p>
<pre><code>Call:
glm(formula = income ~ height + age + educat + married + sex +
language + highschool, family = Gamma(link = log), data = fakesoep)
Dev... | 73,060 |
<p>I'm using a supervised machine learning algorithm on some big data. There is much more features than observations. To reduce the number of features, I would like to do some feature selection. However, there is one thing I'm confused about. May I do the feature selection <em>first</em>, using data from <em>all</em> o... | 73,061 |
<p>For example I have a data set as:
(2042.044,2218.153,3670.893,5149.684,5533.429,7111.183,11041.569,15459.771,783.477,1701.520,40810.770,67905.857)</p>
<p>How do I fit the above data in Burr distribution to compute its parameters in R? fitdist does not provide Burr distribution. Can I explicitly define my probabilit... | 73,062 |
<p>On <a href="http://v8doc.sas.com/sashtml/stat/chap29/sect27.htm" rel="nofollow">this page</a>, I am interested in the section “goodness of fit”, which is near the bottom of the page and contains the table of deviance functions. </p>
<p>The author states that the scaled deviance, i.e. $D^*= \frac{D(y, \mu)}{\phi} $ ... | 73,063 |
<p>In stage 1 we test many SNPs, in stage 2 we try to confirm these SNPs. Usually we start with less sample, but then it's hard to detect a signal. For example, if we can afford 3000 samples, how to allocate these 3000 people in two stages?</p> | 35,249 |
<p>18 people, who have been divided into 2 groups based on the semiquantitative expression of a protein (low vs high).</p>
<p>Group 1 (low protein levels) has 6 people, Group 2 (high protein levels) has 12 people. In Group 1, 5 of the 6 people developed a specific disease, whereas only 2 of 12 in Group 2 developed thi... | 42,173 |
<p>I have non-nested count data that I've interpolated from one area to another based on the proportion of the area that lays in each. This is ZIP codes to counties, so most nest cleanly, with a few around the edges needing to be distributed in this way. I'm aware that it would be better to propagate this uncertainty... | 73,064 |
<p>I <a href="http://stats.stackexchange.com/questions/58532/can-i-derive-the-pdf-fc-from-a-spatial-function-defined-as-cx">now understand how to conduct a change of variables</a> for a marginal PDF.</p>
<p>Now, given two functions that define parameter's spatially: $C_A(x)$ and $C_B(x)$, is it possible to construct t... | 73,065 |
<p>I have a lin-log regression model like </p>
<p>$$Y = b_0 + b_1 \log(x_1 + 1) + e.$$</p>
<p>The distribution of $x_1$ is very skewed, thus I use the natural logarithm to get a more Gaussian like distribution. Because 3 out of 100 values have zero as entry I add a constant c, in my case plus 1, to avoid -Inf. </p>
... | 46,566 |
<p>I am using <code>auto.arima()</code> for forecasting. When I am using any in built data such as "AirPassengers" it is capturing seasonality. But, If I am entering data in any other format (in vector form or from an excel sheet) it is not detecting seasonality.</p>
<p>Is there any specific format in which it detects... | 73,066 |
<p>I am trying to figure out whether from the following graph of the OLS residuals that the linear relationship does not hold, and that probably a cubic relationship would do better? Since both in the beginning as in the middle the variance is larger, and two bends in a regression could lower the variance for these are... | 73,067 |
<p>We have a metric dependent variable (impairment, scale 0-40), and a larger number of symptoms of a mental disorder, each on a scale of 0 (nonexistant) - 3 (very severe). </p>
<p>We try to find out whether symptoms are associated with different levels of impairment. We test this in two steps. First, we use a linear ... | 38,239 |
<p>I am trying to run a regression to model sovereign default risk of EU countries.<br>
My data includes credit ratings (numerical value assigned 0-20), CDS spreads, Bond Yield Spreads, Bond yields, Inflation and GDP per capita. </p>
<p>However, I am a bit confused in terms of setting up the regression. I have to do a... | 35,255 |
<p>We have a set of 60000 files, and a we have a piece of software that attempts to look at each file and determine what date the contents pertain to. We would like to be 99% confident that our software is selecting the correct date 95% +/- 5% of the time. </p>
<p>We manually created 658 tests that each take a file ... | 73,068 |
<p>What are parameters <code>start</code>, <code>etastart</code>, <code>mustart</code> in the <a href="http://stat.ethz.ch/R-manual/R-patched/library/stats/html/glm.html" rel="nofollow">glm() function</a>? I have been looking in the docs and the internet but I have found no clear explanation what this means.</p>
<p>It... | 73,069 |
<p>When I talk with colleagues about qualitative data analysis tools, Atlas.ti and Nvivo are the two names often popping out. However, few persons seem to have really tried both.</p>
<p>After checking companies websites, one important point for me is that Nvivo will soon offer a native Mac OSX version. My university p... | 73,070 |
<p>I am studying the responses of 500 subjects to temperature increase using a linear regression on each degree of temperature (from 10°C to 28°C). Thus, it was possible for me to compute the intercept and slope for each one of the 500 subjects. </p>
<p>I am interested in identifying three groups of individuals that... | 73,071 |
<p>Can anyone suggest me good papers related to housing data mining. I have googled for a while and couldn't find any recent paper. I am assuming that people have stopped doing any mining related to housing data. Isn't anyone working on it anymore?</p>
<p>I am thinking of applying data mining techniques to predict hou... | 73,072 |
<p>I'm trying to fit distributions of time spent on web pages. My goal is to cluster users based on the time spent distribution. My data set looks like following. (p1,p2 and p3 are web pages and time(in seconds) spent on those pages by each user is listed).</p>
<pre><code>user p1 p2 p3
1 10 20 0
2 0 5 7
3 ... | 73,073 |
<p>I am looking for a method to find confidence intervals for NPS (net promoter score). One method was already suggested <a href="https://stats.stackexchange.com/questions/18603/how-can-i-calculate-margin-of-error-in-a-nps-net-promoter-score-result">here</a>. But I am thinking of using bootstrap. Do you think the follo... | 35,261 |
<blockquote>
<p>Let $X$ and $Y$ be independent random variables, each of which is uniformly distributed between $0$ and $1$. Find the probability that $(X−1/2)^2+(Y−1/2)^2≤1/9$. Give at least $8$ correct digits after the decimal point.</p>
</blockquote>
<p>I do not know where to start with this question. Can someone... | 73,074 |
<p>I have two (non-independent) OLS-parameter estimates each with its own standard error. I'm trying to find out what the standard error of the difference of the estimates should be. Can anyone help? Is this too general?</p> | 73,075 |
<blockquote>
<p>A newspaper uses one ton of newsprint every day. It buys its newsprint from a local distributor. This ditributor supplies the newsprint in one-ton rolls at the cheapest price, but unfortunatley its deliveries are erratic. Hence, the number of rolls of newsprint in the newpaper warehouse varies randoml... | 46,588 |
<p>I'm quite an amateur data analyst/modeller trying to teach myself some new techniques. I have a system in which, on the occurrence of an event, two outcomes can occur (either 0 or 1), and a number of prediction models designed to give the probability of the outcome 1, based on previous events. Some of these models a... | 73,076 |
<p>I come to you today because I face a huge problem that I cannot explain.</p>
<p>I have run a multinomial logistic regression (using the mlogit package) on behavioral data. I prepare the data by doing</p>
<pre><code> mlogit <- mlogit.data(Merge, choice = "Choice", shape = "long", alt.var = "Comp",
... | 73,077 |
<p>Suppose we do the following study. We have 2 web-servers (server A and server B) which are processing user requests. Both run on the same hardware, but one of them (server B) uses a slightly different algorithm for request processing. When a user request comes in we have 50/50 chance of processing it on each server.... | 73,078 |
<p><strong>The Problem</strong>
There's a bag with six distinct tokens in it (e.g. a six-sided die). Each token has an unknown value of some real number. A "trial" consists of drawing five tokens (five die rolls) and being told the sum (to clarify, you do know the identifier for each token, just not its value).</p>
<p... | 73,079 |
<p>I'm modeling the effect of a categorical predictor on a binary dependent variable using logistic regression. I'm comparing models with/without the predictor using a likelihood-ratio test.</p>
<p>Two categories of the predictor are associated with values of 1 only (no 0s) for the dependent variable. Regression coeff... | 73,080 |
<blockquote>
<p>Using the Central Limit Theorem , Evaluate $$\lim_{n \to \infty} \sum_{j=0}^{n}{{j+n-1} \choose j}\frac{1}{2^{j+n}}$$</p>
</blockquote>
<p>My solution: Let $\{X_n\}$ be a sequence of iid R.V's each having $Geo(\frac{1}{2})$ </p>
<p>Then $E(X_n)=1$ and $Var(X_n)=2 < \infty,n\in N$ </p>
<p>Also $S... | 73,081 |
<p>I am trying to understand Logistic Regression in relation to credit scoring model. I wish to understand the significance of "20/ln(2)" in logistic regression. Why and how is it used? </p> | 73,082 |
<p>I am currently monitoring the daily energy consumption of a house since January of this year. That daily consumption depends on several variables, including outdoor temperature, solar irradiance etc.</p>
<p>At regular intervals (once every two weeks) I am changing the algorithm of the heating controller, to see if ... | 46,595 |
<h3>Assumptions:</h3>
<p>In an ANOVA where the normality assumptions are violated, the Box-Cox transformation can be applied to the response variable. The <code>lambda</code> can be estimated by the using maximum likelihood to optimize the normality of the model residuals.</p>
<h3>Question:</h3>
<p>When the estimate... | 35,277 |
<p>I performed both a SVD decomposition and a multidimensional scaling of a 6-dimensional data matrix, in order to get a better understanding of the structure of the data.</p>
<p>Unfortunately, all the singular values are of the same order, implying that the dimensionality of the data is indeed 6. However, I would lik... | 35,278 |
<p>There are often differences between results of Skewness & Kurtosis and normality tests, and I have always doubts if it is better to choose parametric or nonparametric tests (I use SPSS). Sometimes histograms show if distribution looks normal or not, and I noticed that most often S&K are better pointers but w... | 73,083 |
<p>In the examples given at this <a href="https://www.researchgate.net/post/How_to_decide_whether_the_distribution_is_unimodal_or_bimodal_in_grain_size_distribution" rel="nofollow">link</a>, I am not able to decide whether the distribution is unimodal or bimodal. I think it is in between unimodal and bimodal, but I do ... | 46,606 |
<p>I have 2 level Design (DOE) with 4 factors (A,B,C,D). I've already calculated the estimates for each main effect and all the interaction effects.</p>
<p>How can I construct the normal probability plot to see which effects are significant? I have looked at many packages in R for Design of Experiment but cannot find... | 46,607 |
<p>I have a list experiment with N=150. The control group was given 3 factors and the treatment group was given 4 factors, with random assignment to these groups. Each group had to report how many factors apply to them. I've done 18 batches of this experiment. In most of them, the mean for the treatment group is higher... | 46,608 |
<p>I ran annual logisitic regression on time-series datas. The most important independant variable have coefficient that are significant in a lot of years, that's a relief. But the "controlling variables", have non-significant coefficients. I'm far from an expert in stats.</p>
<p>My sample is very small compared to th... | 73,084 |
<p>I am using a Johansen procedure to test for cointegration a vectorial 4-dim vector (timeserie). </p>
<p>First I tested for differential stationarity of each individual vector, all of those have a unit root so we are good there. </p>
<p>Then I have to find the optimal number of lags as to test for cointegration usi... | 73,085 |
<p>I once heard that, generative learning, discriminative learning and max-margin learning can be separated in terms of their respective definition of loss function. I am not sure how to achieve that?</p> | 35,283 |
<p>I know that it's not right to enter variables having multicollinearity (high correlation) into a regression analysis. But if I'm using <strong>backward stepwise regression</strong> could I add all the highly correlated predictors and expect the best predictors to remain in the model at the end or the analysis could ... | 73,086 |
<p>I am an occasional data-mining methods user and I simply wonder what are the main challenges and research directions for method designers. </p>
<p>Thanks for your expertise,</p>
<p>Peuhp</p> | 35,284 |
<p>I am self-studying <a href="http://www.stat.columbia.edu/~gelman/arm/" rel="nofollow">this book</a> and need assistance on one of the exercises, specifically 3.9.2:</p>
<p>Suppose that, for a certain population, we can predict log earnings from log height as follows:</p>
<ul>
<li>A person who is 66 inches tall is ... | 46,615 |
<p>I am using rlm in the R MASS package to regress a multivariate linear model. It works well for a number of samples but I am getting quasi-null coefficients for a particular model:</p>
<pre><code>Call: rlm(formula = Y ~ X1 + X2 + X3 + X4, data = mymodel, maxit = 50, na.action = na.omit)
Residuals:
Min ... | 46,616 |
<p>The combination of a $\Gamma$-distribution with the log-link function in a generalized linear model can be a useful model. However, in my experience the iterative weighted least squares (IWLS) algorithm (specifically, the implementation in R via <code>glm</code>) does not always converge. </p>
<p>The log-link is no... | 18,849 |
<p>I have 15 supervisors who have ranked 21 employees from 1 (best) to 21 (worst), but the rankings are strictly ordinal-there is no interval data available. Can I compare any two (or more) supervisors' rankings and determine how closely their evaluations are aligned? I'll be using Excel 2010 (or pen/paper) for my ana... | 73,087 |
<p>I have used <code>mlogit</code> package and I am trying to summarize the results I have from my model. I have a question regarding the reference value and will get to that in a moment.</p>
<pre><code>redata.full <- mlogit(no.C~ 1| WR+age+age2+BP+noC.1yr, data=redata, reflevel="0", na.action=na.fail)
no.C = num... | 73,088 |
<p>Suppose an ARIMA(p,d,q) model fits the data very poorly. What are some ways to improve the fit? Is there any way to do it without guessing and checking?</p>
<p><strong>Edit.</strong> I am using auto.arima() to search for an ARIMA model. But it is a poor fit.</p> | 46,626 |
<p>I'm trying to build a model to predict reservations up to 15 days in advance.</p>
<p>So, if I want to predict how many reservations there will be tomorrow, I use historical data of how many total reservations there were on two days prior since when using the model to forecast for tomorrow, today won't be finished..... | 73,089 |
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