question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I'm doing some research into factor analysis and I've hit that barrier where I don't know what search terms to use.</p>
<p>I'm trying to see if something is possible. Basically I have a data set with ~100 numerical variables. Each record also has a target variable which is a category. My ultimate goal is to perform... | 71,931 |
<p>I have used the STDRATE procedure to get the estimates and standard errors for 5 different timeperiods between 1980-2000 in 5 years interval (1980, 1985, 1990, 1995 and 2000). </p>
<p>This means that I have point estimate and 95% CI for $X_1, X_2, X_3, X_4$ and $X_5$ which spans between the years 1980-2000.</p>
<p... | 49,433 |
<p>How do I take the partial derivative of bivariate normal cdf and bivariate normal pdf with its arguments (i.e. $x_{1}$ ,$x_{2}$ , and $\rho$ in the following equations)?</p>
<p>\begin{equation}
y=\Phi(x_{1},x_{2},\rho)
\end{equation}</p>
<p>\begin{equation}
z=\phi(x_{1},x_{2},\rho)
\end{equation}</p>
<p>where $x... | 33,678 |
<p>This question has no practical importance for me, but anyway: I am interested whether we can predict somehow one missing value in a correlation matrix. Obviously, classical regression modeling is not appropriate here. Is there any other way, how we can say something about missing correlation? In addition, does the a... | 71,932 |
<p>Given a time-series of log-return of SP500, then to obtain the volatility process what should we do? Some people say that we need using the ARMA model to withdraw the residual series, then plug this residual series into the GARCH model to obtain the conditional variance process? Or directly plug the log-return plug ... | 71,933 |
<p>I am conducting a logistic regression. However, the Shapiro-Wilk test has determined that one of the X variables is non-Gaussian.</p>
<p>Do the explanatory (X) variables need to be Gaussian? If so what are the usual transformations that can be done?</p> | 71,934 |
<p>I am trying to do some feature selection using correlation. However, I found that my features are not that correlated. The highest correlation was 0.08. So I am not sure if this is a useful thing to do.</p>
<p>I tried to use lasso however, I have huge number of features and when I tried to use lasso, it took like a... | 71,935 |
<p>I have a bunch of features/xs and a bunch of targets ys. I want to run a linear regression on this. I don't know if I should take every y to be independent and learn separate regression models or just a single model with multitargets and xs. What would be the best?</p>
<p>If I have to do with multiple ys how can I ... | 71,936 |
<p>I have a list of sites and a list of survival probabilities associated with those sites. The data looks like this:</p>
<pre><code>Site Probability
A 0.8
B 0.4
C 0.2
...
(14 sites in total)
</code></pre>
<p>Is there any way to test if survival probability varies significantly between sites?... | 71,937 |
<p>Suppose that I have a variable like <code>X</code> with unknown distribution. In Mathematica, by using <code>SmoothKernelDensity</code> function we can have an estimated density function.This estimated density function can be used alongside with <code>PDF</code> function to calculate probability density function of ... | 12,430 |
<p>I am working with a survey dataset which contains hundreds of variables. The item-missing data rate ranges from 0.2% to 10%. In order to retain study units with missing values and to maintain a reasonable statistical power for my analyses, I attempted to do multiple imputation using sequential regression (chained eq... | 71,938 |
<p>I am working with a data set describing a set of US Senators, their votes on a climate bill, and several characteristics of the state they represent. One of the variables, 'imptot', describes the combined importance for their state's economy of <strong>four industries</strong>. These industries cause greenhouse gas ... | 71,939 |
<p>I am currently working on the time series analysis for series Y but I have to use other two variable A and B as an input variable in SAS proc arima procedure. But I am unable to interpret the cross correlation chart and backshift parameters. BackShift 1 for variable A and back shift 2 for variable B. Could anyone he... | 71,940 |
<p>Let's say I have fitted a binary classifier to some data and I'm varying the cutoff value, effectively producing a ROC-curve. Knowing the true proportions of positives and negatives, I can calculate the proportion of data classified as positive, i.e. $TP + FP$ for any given cutoff, and also its corresponding precisi... | 33,685 |
<p>So I have a series of proportions taken weekly for 7 weeks. This is a study of which way spiders were facing. So for example, the first week, 20 spiders were facing out, and 10 were facing in. Now I want to test whether the proportion of spiders facing out was consistent across the 7 weeks. The population of spiders... | 71,941 |
<p>Imagine I have many coins ($>100$), and for each coin I have the data: $(n_{\rm heads}, n_{\rm tails})$ where $\sum(n_{\rm heads}, n_{\rm tails})$ is decreasing for each next coin. Any one of the coins can be unfair ($P({\rm head})\ne 0.5$). Some coins might be an exact copy of any other coin, some might not be. ... | 71,942 |
<p>I'm a postgraduate student, doing a accent perception study, this is my first time using SPSS!</p>
<p>I'm conducting the above tests on my data, where my participants used Likert scales to analyse the personality traits of 2 guises produced by speakers from Devon. Because of this, some of my responses are 'unknown'... | 33,686 |
<p>I am attempting to plot hurdle regression output with an interaction term in R, but I have some trouble doing so with the count portion of the model. </p>
<pre><code>Model <- hurdle(Suicide. ~ Age + gender + bullying*support, dist = "negbin", link = "logit")
</code></pre>
<p>Since I am unaware of any packages t... | 71,943 |
<p>I need to fit a very complex Bayesian hierarchical model and I want to use the adaptMCMC package of Andreas Scheidegger to do the posterior sampling. I can only find the adaptMCMC package reference manual, which doesn't provide a very helpful example of the core sampling function. Does anyone know if there is a more... | 71,944 |
<p>I have a univariate time series consisting of 70,000 observations (power consumption of a building) over equal time increments (15 minutes).</p>
<p>How do I check whether this realization is wide-sense stationary? Note that I don't know the formula of the underlying stochastic process, so I cannot calculate the mea... | 71,945 |
<p>I am trying to understand what could be causing these strange values to appear on applying a Holt model to a vector. The data represents actual sales of an item.</p>
<pre><code>library(forecast)
sdata<-c(1955651,1691857,1617358,1509591,1452025,1387790,1630114,3522984,3322908,2315689,
4044634,11553435,9747305,52... | 36,810 |
<p>I have data from 100 individuals doing a 2AFC under a control and a manipulated setting. I want to compare the means. I initially used a paired t-test. My supervisor noticed the distributions were not normal and recommended me using the Mann–Whitney U test instead of the t-test. However, as far as I can tell, the Ma... | 33,693 |
<p>Can some one tell me when and why to use <code>softmax=true</code> option and <code>entropy=T</code> option?</p>
<p>The model i am trying to build has binary outcome and <code>softmax=true</code> works only when the two outcomes are classified as two variables on its own.</p>
<p>Otherwise <code>entropy=T</code> wo... | 71,946 |
<p>Consider the model
$$
Y_i^{(\lambda)} = \alpha+\beta x_i + \varepsilon_i,\qquad \varepsilon_i,\ (i=1,\ldots,n) \sim \mathrm{i.i.d.}\ N(0,\sigma^2)
$$
where
$$
\begin{align}
y_i^{(\lambda)} & =
\begin{cases}
\dfrac{y_i^\lambda-1}{\lambda(\operatorname{GM}(y))^{\lambda -1}} , &\text{if } \lambda \neq 0 \\[12p... | 71,947 |
<p>I am trying to determine what the most appropriate non-informative priors are for the two parameters of a log-normal distribution (for an accelerated failure time model). I had been working with a normal prior on the mean of the logged data (or log-normal prior on the median), and an independent normal prior on the... | 33,695 |
<p>I've seen this question answered <a href="http://stats.stackexchange.com/questions/51275/what-is-the-difference-in-what-aic-and-c-statistic-auc-actually-measure-for-mo">here</a> but I do not understand the answer. Harrell recommends using deviance based measures. David Hand (referenced in the thread) says that that ... | 71,948 |
<p>I am a beginner in statistics and probability study. Today I came across a new topic called the Mathematical Expectation. The book I am following says expectation is the arithmetic mean of any random variable coming from any probability distribution. But it defines expectation as the product of some data and the pro... | 33,696 |
<p>This may be quite a basic question but I was running a simple linear model and dropping non significant terms until I got to a minimal model. When this was reached, I was obtaining the significance for the explanatory variables that remained also by dropping them one at a time. Now, what I am getting is that one of ... | 49,359 |
<p>I just want to know if its possible to cluster an univariate time series, in order , say, to detect anomalies?</p>
<p>and do you have any online version for denstream code, in Matlab? </p>
<hr>
<p>here is the time series </p>
<blockquote>
<p>+0003;+0004;+0004;+0005;+0004;+0004;+0004;+0003;+0003;+0004;+0003;+00... | 33,699 |
<ol>
<li>Are there ways to analytically derive the moments of a function of
sample moments? For example, my recent question here hasn't been
addressed satisfactorily yet here: <a href="http://math.stackexchange.com/questions/925131/mean-of-squared-sum-of-squared-errors/925217#925217">link</a></li>
<li>Do the moments of... | 14,738 |
<p>We want to create indicators for event based clinical conditions, like migraine or epilepsy.
This conditions are characterized by events which can happen with various frequencies and we would like to classify patients according to the frequency of events.</p>
<p>The problem is that the frequency of the events is co... | 71,949 |
<p>I have hard time to understand that what is the null hypothesis in the definition of Sensitivity and Specificity <a href="http://en.wikipedia.org/wiki/Sensitivity_and_specificity" rel="nofollow">here</a>? I'm student of Statistics and from my little knowledge in this field I can see that the here null hypothesis sho... | 71,950 |
<p>Just as an example Scotland has poll to decide whether they need to be independent from UK or not. Here is BBC's summary of different polls:</p>
<p><a href="http://www.bbc.com/news/events/scotland-decides/poll-tracker" rel="nofollow">http://www.bbc.com/news/events/scotland-decides/poll-tracker</a></p>
<p><img src=... | 33,702 |
<p>Below is the information about the weight of coffee (in thousand kg) sold at two locations (location1 and location 2)</p>
<pre><code>26.3, 26.5, 16.2, 16.2, 26.4, 16.8, 16.1, 16.9 (8 shops)
44.4, 44.7, 34.9, 54.1, 44.8, 22.6, 36.4 (7 shops)
</code></pre>
<ol>
<li>Find the 95% confidence interval for the differenc... | 33,703 |
<p>A regression showed a strong linear relationship between a car's age (measured in months) and a drop in its price from new. </p>
<p>Your friend sees these figures and thinks he can sell his car at a price obtained from this regression analysis. What would you say to him?</p> | 33,704 |
<p>Can anyone help me to evaluate $\int_{\alpha}^1 e^{-(c \cdot ln(1/x))^s} dx$,
where $0 \leq \alpha \leq 1$ and $s$ is real. </p>
<p>I tried changing variables, integration by parts etc. and got no clue how to handle this. </p> | 14,748 |
<p>I ran a paired T-test to determine the mean difference between pre and post intervention of one of the variables in my study. However the test was not run as the SPSS output showed "the correlation and t cannot be computed because the standard error of the difference is 0". </p>
<p>What should I do to get the p-val... | 43,946 |
<p>Suppose I am a consultant and I want to explain to my client the usefulness of confidence interval. The client says to me that my intervals are too wide to be useful and he would prefer to use ones half as wide.</p>
<p>How should I respond? </p> | 43,949 |
<p><a href="http://uk.answers.yahoo.com/question/index?qid=20080702080708AAsRZpt" rel="nofollow">Here</a> is a link that describes the formula to find the mode of grouped data.</p>
<p><a href="http://www.tutors4you.com/modegraphically.htm" rel="nofollow">Here</a> is a link that gives a graphical method to finding the ... | 43,950 |
<p>[Cross post from <a href="http://math.stackexchange.com/q/8830/2949">here</a>, figured this community may be more relevant]</p>
<p>I am working in the field of machine learning, and I have come across a few papers that show relationships between Gröbner bases and discrete probability. So I come here for help.</p>
... | 33,706 |
<p>Hello
I have two problems that sound like natural candidates for multilevel/mixed models, which I have never used. The simpler, and one that I hope to try as an introduction, is as follows:
The data looks like many rows of the form </p>
<p><code>x y innergroup outergroup</code></p>
<p>where x is a numeric covaria... | 71,951 |
<p>It seems to me that the standard way to deal with the problem of testing wether two multivariate samples of categorical data have the same joint probability distribution is to employ a goodness-of-fit test, like the chi-squared one: assuming that the frequencies of one sample (normalised counts per combination of va... | 71,952 |
<p>I'm running an experiment with an e-learning system using a repeated measures with crossover design. </p>
<p>Subjects are shown two videos on a web page. In one session, a feature (a table of contents) is enabled, while the other session is a control:</p>
<pre><code>C=Control F=Feature
subject pretest1 video... | 71,953 |
<p>I'm estimating a GLM with a continuous variable $X_1$, a dummy variable $X_2$ and the interaction term $X_1*X_2$. </p>
<p>After my understanding, when interpreting the coefficient of $X_1$ you should assume the value of zero for $X_2$, i.e. also for the interaction term. </p>
<p>Now a colleague suggested that if I... | 37,815 |
<p>What is the typical method for creating a probabilistic output from an All-vs-All or One-vs-All multi-class classifier? For example, if my problem has 3 classes (Class1, Class2, Class3) and I build an AVA classifier, then I have a classifier for:</p>
<ul>
<li>Class1 vs Class2 ($f_{12}(x)$)</li>
<li>Class1 vs Class3... | 71,954 |
<p>Im a surgeon who's trying to compare two diagnostic tests that are used to diagnose appendicitis. Two diagnostic tests were applied on 150 patients and the results were compared to a gold standard. I understand that the sensitivities and specificities can be compared by using a McNemars chi square test. But what ab... | 71,955 |
<p>I've seen different error metrics used in the Kaggle competitions: RMS, mean-square, AUC, amongst others. What's the general rule of thumb on choosing an error metric, i.e. how do you know which error metric to use for a given problem? Are there any guidelines?</p> | 33,709 |
<p>I asked a variation of this question, but I want to be more direct.</p>
<p>Take the exact same Triple Exponential Smoothing Model (Holt-Winters with a moving level, trend, and seasonal component)---</p>
<p>Would or would not --- the smoothing parameters alpha, beta, and gamma (determining the weight of recent data... | 33,710 |
<p>I have a data set with two columns, the first of which is to be used as a response variable and the second of which is to be used as a predictor variable. The predictor variable, however, is populated by integer values, many of which are zero. When I place data points for the predictor and response variables into g... | 71,956 |
<p>I know this is a touchy subject, so I'll proceed with caution... </p>
<p>I am building regression models for some hundreds of thousands of data files containing only two columns. The sensor collecting these data is not great and sometimes things interfere with the measurement, so the data are extremely noisy; a typ... | 71,957 |
<p>I am trying to explain datasets gathered from simulation with various regression models. Linear regression seems not applicable because my data after transformations still violate
the assumptions for linearity, normality of errors etc.</p>
<p>I have built several non-parametric models (splines, regression trees, SV... | 71,958 |
<p>Let's assume that one has the following inputs and corresponding outputs:</p>
<pre><code>x1 = (a,b,c) with corresponding output y1, which is a number.
x2 = (d,e,?) with unknown output
x3 = (?,?,g) with known output y2, which is a number
</code></pre>
<p>and so on.</p>
<p>So, by "incomplete input data" I don't jus... | 33,712 |
<p>Would it make sense to apply a measure of association test like Cramér's V on a 1xk table? </p>
<p>I am a bit puzzled because in the literature phi and Cramér V are normally used on 2x2 or bigger contingency tables, but while I was looking for some more info, I found the following statement on Wikipedia:</p>
<p>"C... | 71,959 |
<p>I want to test my classifier performance using a permutation test. I know how to test one actual value against a null distribution of values generated by randomly reassigning labels to my two classes.
However, in this case, I don't have one value but also a distribution of performances on correctly labelled data, be... | 972 |
<p>I am fitting a single exponential decay formula with three parameters (a,b,c): y ~ $a \exp(-xb) + c$ using the LAD cost function: $ \min \sum |(y - f(x))| $. $x$ is in units of time (as is $b$), and $a$, $c$ are unitless. Measurements are taken far enough out in time that the last $y$ is effectively only noise from ... | 33,713 |
<p>I ran a big Neural Network with the initialized weight matrix learned by RBM (Restricted Boltzmann Machine), and the result shows something like this.</p>
<p>On train dataset<br>
The best precision: 0.79564. And the best recall: 0.75685. The best f1: 0.775760<br>
On test dataset<br>
The best precision: 0.73... | 71,960 |
<p>I have a question about which prediction variance to use to calculate prediction intervals from a fitted <code>lm</code> object in R. </p>
<p>For a certain multiple linear regression model I have obtained an error variance with leave-one-out-cross-validation (LOOCV) by taking the mean of the squared difference betw... | 71,961 |
<p>I am conducting a two-sample test (1-way ANOVA with 2 treatments), and the goal is to estimate the ratio of cell means assuming that the data are lognormal. A simple approach is to log the response and fit a model </p>
<p>$\log Y = b_0 + b_1 * X$</p>
<p>and then estimate the ratio as</p>
<p>$R = e^{b_1}$</p>
<p>... | 33,715 |
<p>I am interested in a general question about research design, but I will explain it on a specific example. </p>
<p>Suppose I want to determine if one group of people has higher heart rate than the other group. Let's consider two methods to do that, two scenarios:</p>
<p>Scenario 1: we get <strong>one measurement</s... | 33,716 |
<p><img src="http://i.stack.imgur.com/Lw0BS.png" alt="model"></p>
<p>This is my model adapted from a study. I want to know whether I can only study it as a path analysis without studying mediation effect (1 $\longrightarrow$ 5 direct effect, as well as indirect effect) by just checking effect of one variable effect on... | 71,962 |
<p>Assume I have a regression type model. Are their any statistical and/or substantial <strong>reasons NOT to include a two-way interaction which consist of a percentage and the corresponding population size</strong>.</p>
<p>An example would be to include an interaction between the percentage of households which own a... | 71,963 |
<p>I am trying to analyze a dataset in which there are three measures on patients within areal units, however I am having trouble in how I am thinking about random/fixed effects and including covariates at different levels of the model.</p>
<p><strong>Dataset</strong></p>
<p>Dependent variable:</p>
<ul>
<li>Presence... | 71,964 |
<p>I am stuck on a research problem and do not know what kind of methods to use. I hope people in this forum can give me some good ideas, I've always had good brainstorming sessions here. </p>
<p>My problem is that I have a laser and a stack of thin films made up of three different materials. If I shoot the laser at t... | 71,965 |
<p>Let $X$ and $Y$ be two random variables, such that the (average) mutual information is very small:
$$ 0 \le I(X;Y) \le \epsilon \ll 1$$</p>
<p>In this case, we say that $X$ and $Y$ are <em>almost</em> independent. Now, can we deduce something like:
$$\forall x,y \quad \Pr[X=x,Y=y] \le \Pr[X=x]\cdot\Pr[Y=y] + \delta... | 71,966 |
<p>Say we want to perform a logistical regression analysis (although my question pertains to regressions in general) on sports results to determine the effects of various factors on who wins and who loses. We have the background information we want on the teams and players and now just need a random sample.</p>
<p>So... | 33,719 |
<p>It is easy to show using matrix algebra when least squares will produce bias.</p>
<p>\begin{equation}
\begin{split}
\text{E}[B]& = \text{E}[(X'X)^{-1}]\times\text{E}[X'Y] \\
& = \text{E}[(X'X)^{-1}]\times\text{E}[X'(XB +\epsilon)] \\
& = \text{E}[(X'X)^{-1}]\times\text{E}[X'XB] + \text{E}[(X'X)^{-1}]\t... | 33,721 |
<p>Does the term "statistical inference" include only hypothesis testing or does it also include point estimation, interval estimation etc.</p>
<p>Authoritative references will be greatly appreciated. </p> | 71,967 |
<p>I am interested in using the R package MatchIt to preprocess my data as to obtain matched groups based on a predefined treatment variable. However I am facing a few issues. </p>
<p>The first issue is that my data contains many covariates (approximately 80) in addition to the treatment variable. Many of these covari... | 71,968 |
<p>I have $N$ Bernoulli variables, $X_1,...,X_N$ and $X_i\sim B(1, \pi_i)$, $\pi$ is known for each $X_i$, and $Y=X_1+...+X_N$, now I need to get the destribution of $Y$.</p>
<p>If $X_i$ and $X_j$ are independent when $i\ne j$, then I can use the simulation:</p>
<pre><code>1. Generate X1, ..., XN via their distributi... | 71,969 |
<p>I am trying to predict expert ratings. They were asked to assign confidence among five possibilities: variables <code>t1</code> through <code>t5</code>.</p>
<p>I have a training set for which text allows me to predict these probabilities.</p>
<p>Is there something that I'm not considering for a model of the kind:<... | 71,970 |
<p>I am trying to understand cross-validation for ordinal logistic regression. The aim of the game is to validate the model used in an analysis...</p>
<p>I first construct a toy data set:</p>
<pre><code>set.seed(1)
N <- 10000
# predictors
x1 <- runif(N)
x2 <- runif(N)
x3 <- runif(N)
# coeffs in the model... | 71,971 |
<p>I'm taking an Intro to Bayes course and I'm having some difficulty understanding predictive distributions. I understand why they are useful and I'm familiar with the definition, but there are some things I don't quite understand. </p>
<p><strong>1) How to get the right predictive distribution for a vector of new ob... | 71,972 |
<p>i hope, you dont need data for this problem, because i believe i am just making a stupid syntax error. The following code:</p>
<pre><code>ggplot()+
geom_point(data=sites, aes(x=NMDS1, y=NMDS2, shape=group), colour="grey") +
geom_point(data=species, aes(x=NMDS1, y=NMDS2, color=phyla), size=3, shape=20) + scale... | 71,973 |
<p>In my system I ask $n$ people to rate [1,5] $m$ objects (e.g. films).
I'd like to get a measure of the inter-subject concordance, i.e. how much the users agreed overall, not just on a particular object but on all of the objects.</p>
<p>I know that <a href="http://en.wikipedia.org/wiki/Kendall%27s_W" rel="nofollow">... | 33,728 |
<p>I am interested in a measurement or index that will tell me if a curve is more convex or concave versus a straight line. </p>
<p>This curve is sampled in n points and I know the x and y coordinates of these points. </p>
<p>The straight line I am comparing this curve with is a line that goes through the first and l... | 71,974 |
<p>I'm using the neuralnet in R to build a NN with 14 inputs and one output. I build/train the network several times using the same input training data and the same network architecture/settings. </p>
<p>After each network is produced I use it on a stand alone set of test data to calculate some predicted values. I'... | 71,975 |
<p>I’m working on a data set in order to evaluate the impact of drying on sediment microbial activities. The objective is to determine if the impact of drying varies among sediment types and/or depth within the sediment.</p>
<p>The experimental design is as follows:</p>
<ul>
<li>The first factor <strong>Sediment</str... | 71,976 |
<p>I'm using <code>Scikit-Learn</code>, which has <a href="http://scikit-learn.org/stable/modules/generated/sklearn.cluster.MiniBatchKMeans.html" rel="nofollow">an implementation of <code>MiniBatchKMeans</code></a>. I'm very inexperienced with ML, so I'm wondering how (if there is a way) I can adapt <code>MiniBatchKMea... | 71,977 |
<p>I am having performance issues using the <code>MCMCglmm</code> package in R to run a mixed effects model. The code looks like this:</p>
<pre><code>MC1<-MCMCglmm(bull~1,random=~school,data=dt,family="categorical"
, prior=list(R=list(V=1,fix=1), G=list(G1=list(V=1, nu=0)))
, slice=T, nitt=iter, ,burnin=burn, verbo... | 71,978 |
<p>I have been looking at Treemapping as a potential data visualisation technique. </p>
<p>Ref: <a href="http://en.wikipedia.org/wiki/Treemapping" rel="nofollow">Wikipedia article on Treemapping</a></p>
<p>While popular in many visualisations, they don't seem to me to be effective at conveying information. This is be... | 71,979 |
<p>I have a general statistical question. Three schools A, B, and C have 0.23, 0.56, and 0.8 fraction of female teachers. The upper and lower confidence intervals (CI) for the three schools can be tabulated as shown below:</p>
<pre><code>school female_instructors upper_CI lower_CI
A 0.33 0.53 ... | 71,980 |
<p>Let's say I have some data on the amount of money spent on tv ads and total revenue from all sales. The data is available for three separate month.</p>
<pre><code> Jan Feb March
$ spent on tv ads 100 110 150
total sales revenue 1000 1000 1500
</code></pre>
<p>The p... | 360 |
<p>I have developed a proof of concept system for sound recognition using mfcc and hidden markov models. It gives promising results when I test the system on known sounds. Although the system, when an unknown sound is inputted returns the result with the closest match and the score is not that distinct to devise it is ... | 71,981 |
<p>Can anyone please write out the model of the ARIMA(1,1,0)x(1,0,0) with AR(1) coef 0.0902 SAR(12) coef 0.107 constant 0.15. Am really confused with how the model should look like</p> | 49,885 |
<p>I want to meta-analyse some studies which I've already collected and review. However, the studies did not used control groups, due to the types of questions used. How can I do the meta-analysis or which software can I use?
Briefly my problem is as follows:
I reviewed studies which the goal was to evaluate the percep... | 71,982 |
<p>I am trying to test this property of pareto distribution: Let f(x) be a pareto distribution</p>
<p>$$
f(x)=\alpha \frac{x_m^\alpha}{x^{\alpha+1}}
$$</p>
<p>so we have the cdf that is</p>
<p>$$
CDF(x)=\int_{x_m}^{x}\alpha \frac{t_m^\alpha}{t^{\alpha+1}}dt=1-\frac{x_m^\alpha}{x^\alpha}
$$</p>
<p>then the probabili... | 33,738 |
<p>Suppose that $X_1,...,X_n$ is an iid random sample from a Poisson distribution with mean $\theta$. I would like to prove that there exists no unbiased estimator of $\frac{1}{\theta}$. </p>
<p>To do so, I will let $\delta(X)$ be an estimator of $\frac{1}{\theta}$. </p>
<p>Then, I'd like to equate the expectation of... | 71,983 |
<p>My data is a table of cosines and I want to analyze it with hclust, which works on squared Euclidean distances.</p>
<p>shall I do:</p>
<p>d <- dist(mydata, method = "euclidean")
fit <- hclust(d, method="ward")</p>
<p>or rather:</p>
<p>d=(dist(mydata))^2<br>
fit <- hclust(d, method="ward")</p>
<p>I don'... | 71,984 |
<p>I am looking for an algorithm or function to look at the difference in reaction times after negative feedback. The problem is that I need to consider just the times in which negative feedback came after 3 positive feedbacks and no all the participants have the same number of negative feedback (or losses)
Any idea?
T... | 21,401 |
<p>I'm trying to run a normality test on the residuals after fitting a mixed-effect model (with lmer). I read that the Shapiro-Francia test can deal with data with more than 5000 observations (I have more than 8000), but when I run it I get an error:</p>
<pre><code>sf.test(resid(dat.lmer11))
</code></pre>
<p>Error i... | 71,985 |
<p>In a traditional filtering context, you'd analyse polls coming in with something like</p>
<pre><code>mu[i] <- alpha[date[i]]
prec[i]<- SampleSize[i]/(alpha[date[i]]*(1-alpha[date[i]])
y[i] ~ dnorm(mu[i],prec[i])
</code></pre>
<p>If the surveys are observed with rounding, this <em>usually</em> won't make a di... | 71,986 |
<p>pls correct me if i'm wrong. of the econometrics' literature i've read so far, most mentioned heteroskedasticity is not a major problem empirically but multicollinearity would pose a greater concern to researchers and that data transformation would improve empirical results but not completely remove heteroskedastici... | 44,809 |
<p>We have prospective data from an observational registry and wish to consider the affects of a gene on time to cardiovascular events. The data includes standard data like age, gender, ... and also the date(age) of a cardio event.</p>
<p>In general terms what are the conditions/assumptions/requirements of a starting ... | 71,987 |
<p>Does 'corr' function in Matlab consider correction for tied ranks while calculating Spearman correlation coefficient?
Thanks.</p> | 71,988 |
<p>Suppose you have a bag of 100 coins of which 1 is biased with both sides as Heads. You pick a coin from the bag and toss it three times. The result of all three tosses is Heads. What is the probability that the selected coin is biased?</p>
<p>My answer:-</p>
<pre><code>P(selecting a biased coin) = 1/100
P(getting ... | 71,989 |
<blockquote>
<p>Given two column vectors $X = (x_1, \dots, x_n)'$ and $Y = (y_1, \dots, y_m)'$ of random variables with finite second moments, canonical-correlation analysis seeks vectors $a$ and $b$ such that the random variables $a' X$ and $b' Y$ maximize the correlation $\rho = \operatorname{corr}(a' X, b' Y) = \d... | 33,747 |
<p><br>
I have no math or stats background, so this may be a real dumbo question.<br>
I'm developing a time estimation app which would let user enter her worst case and best case estimates, and then select a probability curve which she feels looks realistic. </p>
<p>I needed to draw some kind of curve that sums up to... | 71,990 |
<p>I want to measure the correlation between two 1D point processes $x$ and $y$. Ordinarily I could use the bivariate K-function</p>
<p>$K(t) = \frac{T}{n_xn_y} \sum_{i=1}^{n_x} \sum_{j=1}^{n_y} w(x_i,y_j) I[d(x_i,y_j)<t]$</p>
<p>where $n_x$ is the number of observations in $x$ and $n_y$ is the number of observati... | 71,991 |
<p>I'm working with a two-state process with $x_t$ in $\{1, -1\}$ for $t = 1, 2, \ldots$</p>
<p>The autocorrelation function is indicative of a process with long-memory, i.e. it displays a power law decay with an exponent < 1. You can simulate a similar series in R with:</p>
<pre><code>> library(fArma)
> x&l... | 71,992 |
<p>I am reading the second edition of Categorical Data Analysis by Alan Agresti, and somehow stuck in the following second paragraph:
<img src="http://i.stack.imgur.com/ahQDT.png" alt="enter image description here"></p>
<p>I don't quite understand why $\beta\pi(\hat{x})(1 - \pi(\hat{x}))$ will give the probability whe... | 44,725 |
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