question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I am interested in looking for periodicities in a several day long recording of electrical activity. The traces present a very steady baseline over which, from time to time, some short events (300-500 ms) appear (hence the <em>sparse</em> in the title, although I am not sure it is the right term to use).</p>
<p>Now... | 37,545 |
<p>I am trying to understand how cdplot in R behaves, but I am missing something. When I copy/paste the following example given in the documentation for cdplot:</p>
<pre><code>> fail <- factor(c(2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1,
1, 2, 1, 1, 1, 1, 1),
levels = 1:2, labe... | 37,546 |
<p>I have 5 measures repeated 3 times under 3 different scenarios (conditions). The measures are survey questions and participants use a visual analogue scale to mark a response from 0.0 to 15.0. Thus the same 5 measures (questions) are repeated for each of the 3 scenarios (conditions) making 15 measures in total. I... | 69,157 |
<p>I'm trying to devise a model to rank a number of links according to their popularity. The links refer to upcoming events and job offers, and ideally I'd like to have a reasonably simple model that, given the values of some covariates such as the number of clicks on the link and the number of days remaining till the ... | 69,158 |
<p>I have an optimization algorithm that optimize numbers of neurons, early stopping (stopping after X) and best fractures of an binary classification problem with (<code>patternnet</code> and <code>feedforwardnet</code> with threshold of 0.5). Besides it I use 5-fold cross validation in every iteration of optimization... | 30,072 |
<p>In an experiment, 25 subjects (Group A) are assigned to play an adventure game (with audio and non-audio) while another 25 subjects (Group B) are assigned to play a strategy game (with audio and non-audio). Each game has two levels (audio and non-audio). </p>
<p>The independent var are:
(i) groups (A and B)
(ii) ... | 69,159 |
<p>Can the approximating distributions for various factors in Expectation propagation be different distributions but still from the exponential family. For example, I have the following posterior form:</p>
<p>$$
p(w, \lambda, \phi) = p(\phi)p(\lambda)p(w|\lambda) \prod_{i}p(y_{i}|w, \phi, \lambda)
$$</p>
<p>So, I nee... | 69,160 |
<p>I cannot figure out how I will reorganize and run my data for discrete survival analysis. I have 1169 farms repeated from 2001 to 2010 and I measure years in low income but poverty is not death. So spss measures 10*1169= 11690 cases and no 1169. </p> | 17,851 |
<p>I have a p-value that I generate via resampling.</p>
<p><strong>Resamples = 5000</strong></p>
<p><strong>Positive findings = 1000 positive findings</strong></p>
<p><strong>P-value = 1000/5000 = 0.2</strong></p>
<p>How can I compute the 95% confidence interval for this p-value?</p>
<p>I would assume it's a funct... | 69,161 |
<p>I have a continuous response variable $Y$ that I have broken down into four categories, {Low, Medium, High, Very High}. I'd like to model $Y$ against a binary variable $X$. Calculating the proportion of $X=1$ for each of the four categories, I notice that the proportion of $X=1$ is low in the first and last category... | 29,494 |
<p>I just did a binary linear regression in R with a dataset that has 100000 lines. The output of the regression is, that almost every parameter is highly significant. I wouldn't expect that when I look at the <a href="http://picpaste.com/yGsn701X.png" rel="nofollow">boxplots</a>. Did I do something wrong in my code or... | 49,823 |
<p>I was trying to understand the parallel machine learning using Proximal SVM. The implementation I'm following is from <a href="http://atbrox.com/2010/02/08/parallel-machine-learning-for-hadoopmapreduce-a-python-example/" rel="nofollow">atbrox.com</a>.</p>
<p>It was a no-brainer to execute the python script and get ... | 69,162 |
<p>Before I start be easy on me I am not a stats person - I am
just on the quest for information :-)</p>
<p>I was tasked to generate many graphs for someone who wanted to see if the data presented with a bell shape curve vs a graph with > 1 peak - this was no biggie but silly me I thought maybe it would be easier to ... | 69,163 |
<p>I have a data set of prices, these prices vary across time and across area. I have 18 areas with 32 time periods. </p>
<p>What i want to do is forecast these prices, i have found that a AR(3) process fits the data for each area using first difference.
\begin{equation}
\Delta \hat{y}_t = \hat{\beta}_0 + \hat{\beta}_... | 69,164 |
<p>I am no expert in statistics, but I have been asked to implement a VAR model using gradient descent in R. I have written a code that, from what I have been told, it makes sense. However, the estimated parameters are completely different from the ones calculated with gretl. This is more or less what I have been told ... | 69,165 |
<p>I have about 80,000 observations that I collect each day, which include a numeric variable called amount (it's a bid). I often stuff with determining whether a decrease or increase in the amount, be it by hour, day, or week, is meaningful enough that it warrants further analysis. So let's say I have a week's worth o... | 69,166 |
<p>I'm researching the behaviour of a bird called Brent Goose. I plan to collect data on 100 individuals of geese. My response variable is divided into four categories: feeding, walking, aggression and other. I plan to watch a bird for 5 minutes, and record the total proportion of that 5 mins that is spent feeding, wal... | 29,496 |
<p>I'm wondering if you could quickly advise on the best statistical analysis for my data.</p>
<p>I have a designed experiment with 12 plots within one larger area. This area was blocked into 6 to overcome issues of natural gradients present there, so there are 2 plots in each block.</p>
<p>Treatment 1 is a two leve... | 29,497 |
<p>I wonder if I'm lacking the terminology to phrase this question: I would like to model, in <strong>Excel</strong>, the risk of a fairly <strong>rare event</strong>, E, happening over time, where time is divided into chunks called periods, each with n trials. So the event has a low probability (p < 0.1%) of occurr... | 29,499 |
<p>From a survey I have the following data:
44 questions are supposed to measure 11 variables (underlying theory, 4 questions per variable). These 11 variables are supposed to fit into two categories (underlying theory, 5 variables category A, 6 variables category B). I am unsure how to test this. I was advised to use ... | 69,167 |
<p>I am using the Cox regression model to forecast failures of machines. I have several possible covariates. I ran the analysis in SPSS. The method I used to add covariates was backward stepwise (Wald).</p>
<p>My question is that after I got the results, which is the table 'Variables in the Equation' (see below), I ca... | 29,500 |
<p>I would like to show that a new biomarker (let's say percent tumor volume reduction at 3 weeks of treatment estimated with automatic methods) performs better than an old one (same measure, but based on manual volume measurements) to distinguish groups or predict outcome. I have these different settings:</p>
<ol>
<l... | 69,168 |
<p>I have a question</p>
<blockquote>
<p>How would you interpret the odds ratios for a continuous variable?</p>
</blockquote> | 29,503 |
<p>In Larry Wasserman's <a href="http://www.stat.cmu.edu/~larry/=stat705/" rel="nofollow">lecture notes</a> on $o_{P}$ and $O_{P}$, I am not able to follow the derivation of the following example in <a href="http://www.stat.cmu.edu/~larry/=stat705/Lecture2.pdf" rel="nofollow">page 9</a>. </p>
<p>Consider $m$ coins wit... | 69,169 |
<p>I have two values of SD calculated from paired samples of size $n=10$.</p>
<p>Results are:</p>
<ol>
<li>Pre test - mean=29.1 and SD=19.05</li>
<li>Post test - mean=34.9 and SD=16.74</li>
</ol>
<p>How do I calculate the SD?</p> | 69,170 |
<p>The way I understand the Naive Bayes estimators is that the characteristic (or naive) assumption is that all Features are conditionally independent. </p>
<p>Now on top of this assumption, for continuos features it is also assumed that they are Gaussian distributed. My question is whether this is something inherent ... | 49,824 |
<p>Dynamic time warping is a technique to find an optimal alignment between two given sequences.</p>
<p>Is there a technique to find an optimal alignment between more than two sequences? Does it as an implementation in python or R? </p>
<p>Thanks.</p> | 69,171 |
<p>I want to calculate the confidence interval for $\lambda$ from a small ($n=10$) set of repeated observations from a Poisson distribution. That is, I have $X_1, \dots, X_{10}$ which I believe are i.i.d. and I want a 95% confidence interval given these observations for $\lambda$.</p>
<p>I know I can use $\bar x \pm 1... | 69,172 |
<p>Since I found an insignificant result, I performed a power calculation in G*Power. But I am not entirely sure if I input the right number in some fields.
My design is a 2(between Ss) x 2(between Ss) design, so I have 2 variables, 4 different conditions (20 participants in each one). I ran an univariate test in SPSS.... | 29,513 |
<p>I read the following statement in this <a href="http://people.su.se/~sehh3288/documents/students/Master%20Thesis%20-%20Kristoffer%20Sahlin%20-%20final.pdf" rel="nofollow">document</a>$^{[1]}$, at the bottom of page 11:</p>
<blockquote>
<p>Too wide A will some times “hide” the burn in part within the converged par... | 69,173 |
<p>Consider: <strong>dataset</strong> defined as
<code>n</code> datapoints <code>x_i</code> in <code>m</code>-dimensional space. And there is a <strong>label</strong> <code>y_i</code> defining one of the classes belonging to <code>x_i</code>. There are let's say <strong>5 classes</strong> 1,2,3,4,5 (and there is <em>t... | 69,174 |
<p>I have two questions.</p>
<ol>
<li><p>I am running an experiment where I am interested in determining the <strong>sample size</strong> required for a certain CI and error, where values range between $<1$ and $>-1$. However, I am only interested in the minimum sample size required as per the sign + or - not as... | 69,175 |
<p>I was asked such a question as "Did you do any consistency check in your daily work?" during a phone interview for a Biostatistician position. I don't know what to answer. Any information is appreciated.</p> | 29,519 |
<p>I am working with biological dataset. I am looking for significantly differentially expressed genes that stand out under effect of 3 different factors (e.x. gut microbiota level has/not, tissue, Lcells has/not). The data is not good so I cannot perform normal ANOVA test to measure effect of all factors at once. So... | 69,176 |
<p>I am working with microbiological data. I want to test how gut microbiota is developing in my samples. I have one base line, which doesn’t have any gut microbiota, and then by day 1 they receive microbiota and I am monitoring the development of microbiota till day 7. The biological question is: How gut microbiota is... | 17,855 |
<p>I am attempting to calculate Orwin's (1983) modification of Rosenthal's (1979) Fail-safe N for my meta-analysis of Odds Ratios. </p>
<p>However, all the equations I am finding are using Cohen's d, which I cannot calculate (I don't have two groups). </p>
<p>I have STATA, SPSS, and MedCalc at my disposal.</p> | 69,177 |
<p>I have the coefficients for a logistic regression model with $25$ independent variables of mixed continuous and categorical types.</p>
<p>Considering one particular categorical independent variable with $2$ levels so that in the linear model we have a term $x_{i1}$ taking a value of either $0$ or $1$ and an associa... | 69,178 |
<p>Because I would like to calculate the sample size for comparing the area under the curve (AUC) of 2 models (cross-sectional study, predictor = continuous variable). Can you point me which function in R solves it.</p> | 69,179 |
<h3>Question:</h3>
<ul>
<li>Is it possible to get log liklihood values for my stepwise glms?</li>
</ul>
<h3>Context:</h3>
<p>I am able to get a logliklihood value using lmer with the following model. My study involves unbalanced repeated females, two sites (females don't exchange between sites), 8 predictors, and a ... | 69,180 |
<p>Is anyone aware of a statistics resource (preferably 20 to 40 pages maximum) that reviews basic stats for people who took statistics classes already?</p>
<p>This resource could be handed out as a refresher to those who need it. The reason why I'm not looking for a book is that I find that people will more likely re... | 69,181 |
<p>Does independence of $X^2$ and $Y^2$ imply independence of $X$ and $Y$?</p> | 5,718 |
<p>I have two datasets from genome-wide association studies. The only information available are the odd ratios and their confidence intervals (95%) for each genotyped SNP.
My want to generate a forest plot comparing these two odds ratios, but I can't find the way to calculate the combined confidence intervals to visual... | 37,634 |
<p>I am currently working with large datasets that have missing data points. My data ranges from the years 1979-2009. I want to choose, by year, the maximum value from that year. Missing values are replaced with a "." </p>
<p>I am currently using the formula:</p>
<p>{=MAX((E13:E2863=1979)*(H13:H2863))}</p>
<p>This a... | 29,525 |
<p>I'm using R to do a chi-squared test on two sets of data to check if they follow a distribution. In the first case the chi-squared statistic given by <code>chisq.test</code> matches the one calculated by hand, but in the other case it does not. </p>
<p>First case</p>
<pre><code>> e1 = c(18, 38, 78, 107, 107, 72... | 69,182 |
<p>sorry if my question may seem rather silly, but I'm not well up on statistics and need a piece of advice. I have some cases in my dataset where respondents have abandoned the survey half-way, so I coded the missing values as 9999 "Refused to answer". In addition, for likert-scale type of items I applied the code 888... | 25,804 |
<p>I'm trying to write my own function for PCA (of course there's a lot already written but I'm just interested in implementing stuff by myself). The main problem I encountered is the cross-validation step and calculating PRESS value (actually doesn't matter which cross-validation I use. It's a question mainly about th... | 69,183 |
<p>I have a question.
Let's say data has been collected for people with jobs and people without jobs.
People with Jobs are represented by 1, people without jobs are represented by 0.</p>
<p>How do you use a least square method to show the proportion of people with jobs or the proportion of people without jobs?</p>
<p... | 69,184 |
<p>Is "unadjusted" basically just simple linear regression whereas "adjusted" is multiple regression? For example, looking at the effect of x on y adjusting for other variables like a, b and c versus not adjusting for them.</p> | 226 |
<p>I used the Logistic function in weka, to predict a binary class. I have used SimpleLogistic before, but Logistic also seem to give me good results. I did want to clarify if I understand some things well on this classifier, pecially about the ridge estimator</p>
<p>Logistic does multinomial logistic regression with ... | 29,529 |
<p>The only source I have for this being possible is <a href="http://en.wikiversity.org/wiki/Multivariate_analysis_of_variance" rel="nofollow">http://en.wikiversity.org/wiki/Multivariate_analysis_of_variance</a>, but this page does not explain why it is possible.</p> | 69,185 |
<p>I am trying to compare two different numerical profiles and determine whether they are the same or not, computing a p-value.</p>
<p>These profiles are composed of 200 values each (each of which corresponds to a particular position in a DNA strand). They do not have any particular distribution so the first thing i t... | 69,186 |
<p>I'm trying to do correlation between two .wav files or two .pcm files using MATLAB.
I just can't figure out how to do that! If anyone can help me I would appreciate it!</p> | 29,531 |
<p>I am having some problem trying to prove that the diagonal elements of the hat matrix $h_{ii}$ are between $1/n$ and $1$.</p>
<p>Suppose that $Range(X_{n,k})=K $ the number of columns of our matrix of data with a constant.⇒$H_{k,k}$</p>
<p>$H=X(X' X)^{-1}X' ⇒ H'=H ;H^{2}=H $</p>
<p>If $y = \beta x + \epsilon ... | 69,187 |
<p>Can someone post a simple explanation of Dempster-Shafer theory? There are lot of links available but the reading material in those sites is academic in nature and time consuming to read and comprehend.</p>
<p>What I'm trying to do is calculate similarity scores between two words. I am using 3 different similarity ... | 29,532 |
<p>I am working on a model relying on an ugly parametrized function acting as a calibration function on a part of the model. Using a Bayesian setting, I need to get non-informative priors for the parameters describing my function. I know that ideally, I should derivate reference or at least Jeffreys priors but the func... | 29,533 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/13810/threshold-for-correlation-coefficient-to-indicate-statistical-significance-of-a-c">Threshold for correlation coefficient to indicate statistical significance of a correlation in a correlation matrix</a> ... | 49,543 |
<p>In Bayesian statistics I see this derivation often. </p>
<p>Given the likelihood function $f(X|\theta)$ and the prior $f( \theta |a, b)$, the author will derive $f(X|a,b)$. The steps in between are considered trivial but I cannot derive $f(X|a,b)$ myself.</p>
<p>Can anyone please provide some hints, perhaps how to... | 17,860 |
<p>I am analysing the effect of deprivation on breastfeeding and am wondering which type of regression analysis I should use. It is area level data. </p>
<p>Deprivation data is available as a score from 0 - 100 (but no scores actually reach either extreme value) or alternatively as ranked data i.e. 1 = most deprived,... | 69,188 |
<p>... (optional) within the context of Google Web Optimizer.</p>
<p>Suppose you have two groups and a binary response variable. Now you get the following outcome:</p>
<ul>
<li><em>Original</em>: 401 trials, 125 successful trials </li>
<li><em>Combination16</em>: 441 trials, 141 successful trials</li>
</ul>
<p>The d... | 69,189 |
<p>Is it possible to use a continuous predictor in Bugs? The simplest way of doing this would be turning the size variable in alligators example from discrete to continuous. </p>
<p>Both Winbugs and JAGS examples use combination of values of covariates as indices as in </p>
<pre><code>X[i,j,] ~ dmulti( p[i,j,] , n[i,... | 39,709 |
<p>I have a time series (X) representing a natural phenomenon (wind speed, measured every 15 minutes) and I have to create similar time series (up to 20, Xdi, i=1,...,20) with the same structure (same average, same standard deviation, same percentiles distribution...) but with a predetermined correlation (about 0.7) be... | 69,190 |
<p>I have a set of sea surface temperature (SST) monthly data and I want to apply some cluster methodology to detect regions with similar SST patterns. I have a set of monthly data files running from 1985 to 2009 and want to apply clustering to each month as a first step.</p>
<p>Each file contains gridded data for 358... | 69,191 |
<p>I am attempting to build a Multinomial Logit model with dummy variables of the following form:</p>
<ul>
<li>The dependent variable represents 0-8 discrete choices.</li>
<li>Dummy Variable 1: 965 dummy vars</li>
<li>Dummy Variable 2: 805 dummy vars</li>
</ul>
<p>The data set I am using has the dummy columns pre-cre... | 39,710 |
<p>This is a bit of a flippant question, but I have a serious interest in the answer. I work in a psychiatric hospital and I have three years' of data, collected every day across each ward regarding the level of violence on that ward.</p>
<p>Clearly the model which fits these data is a time series model. I had to diff... | 69,192 |
<p>I have a difficult one for strong solvers</p>
<p>Can anyone provide us please an example with coding in R of the bootstrapping method in ANCOVA and one in MANOVA</p>
<p>Thank you very much</p>
<p>T</p> | 69,193 |
<p>If $\mathbf {Z}$ is random vector and $A$ is a fixed matrix, could someone explain why $$\mathrm{cov}[A \mathbf {Z}]= A \mathrm{cov}[\mathbf {Z}]A^\top.$$</p> | 69,194 |
<p>I am finding my way around in the different text mining tools, but I can't find the technique that does the following:</p>
<p>Extract out of the follwing advertisement texts</p>
<pre><code>"apartment with bedrooms: 2, bathrooms: 2"
"appartment with 2 bathrooms"
"appartment with 2 beaufitul batrooms"
</code></pre... | 69,195 |
<p>Comparing the density function of two specific samples in R, both areas are clearly different and cannot be equal to one (see graph linked below). I would like both areas equal one on the same graph as to determine easily the set of abscissa values for which the pdf of a sample is larger than the pdf of the other. W... | 69,196 |
<p>I will ask my question beginning by an example (I am novice in stats)
I have a set of probabilities from a given observation A={0.3,0.2,0.001, 0.02, ...}
I want to partition A on subsets or clusters so as each one will contain the closest probabilities. And after, i will be interested in calculating the distances be... | 69,197 |
<p>To preface this, I have a pretty deep mathematical background, but I've never really dealt with time series, or statistical modeling. So you don't have to be very gentle with me :)</p>
<p>I'm reading this paper about modeling energy use in commercial buildings, and the author makes this claim:</p>
<blockquote>
<... | 69,198 |
<p>I would like to use a set of weather-related historical data to fit a time series (let's say 1970-2000, Fourier terms plus ARIMA terms), but then use the fit on recent data (i.e., the last week/month of data) to forecast the upcoming day/week/month. All of the functions that I've found forecast from the endpoint of ... | 69,199 |
<p>I am working with tobacco prevalence data where I am smoking rates at the country level. I and am in the process of adjusting estimates across different frequencies of use(ie, daily versus occasional smokers). There are some surveys which report both of these values (ie, daily smoking = 30%, occasional smoking = 4... | 69,200 |
<p>In unconstrained optimization, covariance matrix $C$ is parameterized in terms of its Cholesky ($C=LL^\prime)$. In other words, the parameter vector $\theta$ involves elements of the lower triangular matrix $L$. Derivative of $-2LL$ with respect to $\theta$ is computed exactly. Hessian at the final-iteration is com... | 45,529 |
<p>I have been trying to impute future monthly climate data based on sets of downscaled data using the AMELIA package. I have monthly precipitation data from 1960-2099 for different geographic regions and I want to impute precipitation data from 2099-2150 using the past trend of precipitation. I want to use bound featu... | 40,721 |
<p>Suppose {$X_n$} a sequence of random variables.
If $\sum_{n=1}^{\infty}P(|X_n|>n)<{\infty}$</p>
<p>Prove that $$\limsup_{n\to\infty}\frac{ |X_n|}{n} \le1 $$ almost surely</p>
<p><strong>What i have done so far:</strong></p>
<p>I thought using the Borel-Cantelli lemma could lead me somewhere, but i didn't ha... | 69,201 |
<p>I have a distribution of observed measurements and I want to compare it to sampled distributions, using R.
I have a program that samples distributions, according to a certain low of probability / constraint. </p>
<p>Suppose I have:</p>
<ul>
<li>$m$ observed measurements</li>
<li>two sets of $n$ samples of $m$ mea... | 69,202 |
<p>What are good classification methods in the case of continuous independent variables (features) and a small training set (particularly where the number of training examples is approximately equal to the number of independent variables)? Here, small means about 50. I am particularly interested in being able to know w... | 29,548 |
<p>Good Day -</p>
<p>I am working with a dataset that is not normal (general ledger information). I am attempting to determine the following:</p>
<ol>
<li>Given it is not normal, what is(are) the best method(s) to determine
variance (e.g., from median or mean) in a meaningful way?</li>
<li>How can I measure how valid... | 23,978 |
<p>I am working on a number of EEG data sets for binary classification. A good example of one is publicly available <a href="https://www.bbci.de/competition/ii/albany_desc/albany_desc_ii.html" rel="nofollow">here</a>.</p>
<p>If you look at what <a href="https://www.bbci.de/competition/ii/results/kaper_iib_desc.txt" re... | 5,362 |
<p>BIC penalizes based on the number of parameters. What if some of the parameters are some sort of binary indicator variables? Do these count as full parameters? But I can combine $m$ binary parameters into one discrete variable that takes values in $\{0,1,...,2^m-1\}$. Are these to be counted as $m$ parameters or one... | 69,203 |
<p>Pardon my ignorance, i am new to Bayesian Analysis.</p>
<p>I am trying to use Normal prior for a binomial likelihood, which of these are most likely candidates ( $\bar{x} $, $ \mu $, $ \sigma $ ) for prior and most likely candidates for constants ? Please advise.</p> | 29,551 |
<p>What is a main difference between RBF neural networks and SVM with a RBF kernel, from a practical point of view?</p> | 69,204 |
<p>I have what I imagine is an elementary question about evaluating statistical significance, but while I know a lot about probability I can't t-test my way out of a paper bag. From here I'm hoping to get a pointer to where I should look for the answer.</p>
<p>I have a machine learning system and a test set of <em>N</... | 24,746 |
<p>Here is my experiment:</p>
<p>I am using the <code>findPeaks</code> function in the <a href="http://cran.r-project.org/web/packages/quantmod/index.html" rel="nofollow">quantmod</a> package:</p>
<p>I want to detect "local" peaks within a tolerance 5, i.e. the first locations after the time series drops from the loc... | 26,561 |
<p>How do I find the distribution of the weighted sum of independent Bernoulli random variables if the weights are non-negative real numbers?</p>
<p>I have N number of independent Bernoulli distributed random variables lets say X1, X2, X3...XN and suppose I have a set of weights W1, W2, W3,...,WN which are non-negat... | 29,555 |
<p>Suppose we have a simple regression model $y=\beta_0+\beta_1x+u$ under Gauss-Markov assumptions, and $u$ has a uniform distribution on $[0,1]$. Find sampling distribution of the $t_{\beta_1}$-statistic. $t_{\hat{\beta_1}}=\frac{\hat{\beta_1}}{se(\hat{\beta_1})}$, where $se(\hat{\beta_1})=\frac{[(\sum\limits_{i=1}^n{... | 39,719 |
<p>I am trying to fit a multi-level model to some longitudinal data that I have. As an example, let's pretend participants had to make 10 basketball free throws, and I measured how long it took them to make each one (in seconds). In this case, the time variable is severely positively skewed because although there is a ... | 29,557 |
<p>I'm trying to reproduce the average predictive likelihood from page 13 (Eq 4.1) from the following paper and I'm struggling to find the function f_M,k(...).
It details more about it on page 14 but I don't know how to actually produce numbers for it.
Any advice or help would be awesome</p>
<p>Paper
<a href="http://w... | 69,205 |
<p>I am measuring the X, Y, Z variables of i subjects in k states, and for each subject and state i am taking j measurements. What is the proper way to test for differences between the k states?</p>
<p>It seems likes a one way repeated measure ANOVA problem, however how should I deal with the fact that in each subject... | 29,559 |
<p>I am evaluating the effect of covariances between series on returns. That is I run the following regression: $$ r_t = \beta_0 + \beta_1\text{Cov}(Y_t,r_t) + ...$$
I have conducted my analysis with both first difference and log(first difference) on the series. That is I can take either $r_t = P_{t+1}- P_{t}$ or $\l... | 69,206 |
<p>I've been doing chi-square tests to see whether there is a correlation between e.g. motivation levels when studying and degree course. With chi-square, it only reveals whether there is a significant difference between degree course and motivation, but not <em>where</em> i.e. it looks like architects are significant... | 69,207 |
<p>When the text simply says that $X_i$ is a J-dimensional random variable, how do I know that it's supposed to have $1 \times j$ or $j \times 1$ dimension?</p>
<p>An example where this matters is Cramer-Wald device, taken from my professor's notes:</p>
<blockquote>
<p>Let $\{X_i\}_{i=1}^n$ be a sample of J-dimensi... | 69,208 |
<p>Is it possible to overfit a logistic regression model?
I saw a video saying that if my area under the ROC curve is higher than 95%, then its very likely to be over fitted, but is it possible to overfit a logistic regression model?</p> | 29,561 |
<p>I am wondering if there exists such a method in machine learning that:</p>
<p>Given a binary classification problem, for each person in the test set the person that most closely resembles this person in the training set acts as a donor for the value; either 0 or 1.</p>
<p>Could someone show point me in a direction... | 29,562 |
<p>I am learning to use HMM and I am trying to solve the following problem. There is a robot moving around the nodes in graph. The robot can move to adjacent nodes with certain probabilities. Each time the robot steps into a new "node", a (noisy) information about the node is generated. That is, I do not know the exac... | 88 |
<p>Consider the following dataset:</p>
<p>OBJECT: 1 2 3 4 ... 15</p>
<p>SFA: 3.5 2.2 4.0 3.6 ... 2.8</p>
<p>rankingA: 3 9 1 2 ... 7</p>
<p>SFB: 3.1 3.1 3.7 3.4 ... 2.7</p>
<p>rankingB: 4.5 4.5 2 3 ... 9</p>
<p>SFC: 3.3 3.0 3.7 3.5 ... 2.1</p>
<p>rankingC: 4 7 2 3 ... 11</p>
<p>real_ranking: 2 8 1 3 ... 9</p>
<... | 69,209 |
<p>I'm fitting a natural spline fit to some data points. I'd like to estimate the prediction error for the predicted value. In linear regression (I agree that natural spline is also a linear regression with a specific type of design matrix), we know:</p>
<p>$\hat{\beta} = (X^T X)^{-1}X^TY \rightarrow \text{ assuming v... | 29,564 |
<p>I am trying to calculate Mutual Information scores for Feature Selection.</p>
<p>I have successfully implemented the Mutual Information to test each feature against the binary response variable. Each feature in my case is an n-gram with values 1(appears), 0(does not appear), and the binary response class takes valu... | 69,210 |
<p>I have been struggling with this for a while. A typical optimisation problem can be viewed as optimising some cost function which is a combination of a data term and a penalty term which encourages certain solutions. And normally there is a weighting term between the two.</p>
<p>In the bayesian setting, this can be... | 69,211 |
<p>Wouldn't any decision tree trained on a training data set have no errors in classification? In other words, wouldn't every data point be classified correctly in the training data set? How would this tie in with the misclassification rate?</p> | 69,212 |
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