question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I came across a picture of an application prototype that finds significant changes ("trends" - not spikes/outliers) in traffic data:</p>
<p><img src="http://i.stack.imgur.com/sGYeF.png" alt="alt text"></p>
<p>I want to write a program (Java, optionally R) that is able to do the same - but because my statistic skil... | 71,137 |
<p>I would like to fit a mixture model to Monte Carlo generated data with probability densities which typically look like those in the attached image.
<img src="http://i.stack.imgur.com/TQw1z.png" alt="typical densities"></p>
<p>It would seem from visual inspection that a normal mixture model might be applicable but o... | 32,442 |
<p>I am attempting to test the goodness of fit for a vector of count data to a binomial. To do so I am using the <code>goodfit()</code> function in the <code>vcd</code> package. When I run the function, however, it returns <code>NaN</code> for the p-value of the Chi-squared test. In my setup, I have a vector of coun... | 32,443 |
<p>I am trying to perform a canonical correlation analysis to investigate the relationship between attitudes (14 variables), perceived consumer effectiveness (6 variables) AND Intention to dine (DV) 14 variables. However when SPSS generates the Manova Output there are no tables on redundancy index and as far as I unde... | 32,445 |
<p>I am a software engineer by trade doing stats in my free time. I am playing around with an implementation of <a href="http://research.microsoft.com/en-us/projects/trueskill/" rel="nofollow">Microsoft's TrueSkill</a> rating system for ranking players and openings in from a data set of ~700,000 Dominion games. I wan... | 43,227 |
<p>I have a collection of $10^5$ essays, each of which on average contains $10^3$ distinct words. There are $10^6$ distinct words in the entire collection. If I index every word what is the mean and median size of the inverted index lists?</p>
<p>My guess is that median would be 1, but I have no clue how without the p... | 43,228 |
<p>My question deals with how to be able to assert that an "improved"
evolutionary algorithm is indeed improved (at least from a statistic
point of view) and not just random luck (a concern given the
stochastic nature of these algorithms).</p>
<p>Let's assume I am dealing with a standard GA (before) and an "improved"
... | 71,138 |
<p>this is my first post. I'm truly grateful for this community.</p>
<p>I am trying to analyze longitudinal count data that is zero-truncated (probability that response variable = 0 is 0), and the mean != variance, so a negative binomial distribution was chosen over a poisson.</p>
<p>Functions/commands I've ruled out... | 32,451 |
<p>I did a study comparing 2 groups on multiple outcomes/characteristics. I am still learning the ropes when it comes to statistics, so I failed to specify to adjust the p-values. Some of the results that came back were significant with unadjusted p-values in the range of p=.00x and p=.0x (less than .05). </p>
<p... | 40,038 |
<ol>
<li><p>In a discrete-time Markov chain, having constructed the transition
distributions, the initial distribution should not affect the
limiting distribution (when it exists) in theory. So in MCMC, how
to choose the initial state should not affect that the distribution
of $X_n$ will converges to the target distr... | 32,454 |
<p>I have a base signal which is a wave with (fairly) consistent shape and known frequency. On top of that signal is some uniformly distributed additive noise (wave goes from -1 to 1, noise is uniformly distributed from -0.025 to +0.025 on any given sample)</p>
<p>We sample at a specified rate (48K frames/second). <... | 71,139 |
<p>What other techniques can be used in place of a Logistic Regression model?</p>
<p>Also is there any other method besides MLE for estimating the Logistic Regression parameters?</p> | 71,140 |
<p>If I calculate the median of a sufficiently large number of observations drawn from the same distribution, does the central limit theorem state that the distribution of medians will approximate a normal distribution? My understanding is that this is true with the means of a large number of samples, but is it also tr... | 49,873 |
<p>I was trying to understand two different sampling schemes in terms of independence of 2 categorical variables.</p>
<p>Scheme 1:
I have an infinite population where each member poses with two attributes. Those attributes are basically realizations from two independent binary variables (with equal success probabiliti... | 43,243 |
<p>I have the following problem:</p>
<p>Y = X + e</p>
<p>with</p>
<p>Y = Total reaction time (noisy signal)</p>
<p>X = selection time (signal)</p>
<p>e = discrimination time (noise)</p>
<p>I am interestend in the distribution for X and have only samples for Y and e. The experiment had unpaired samples for Y and e... | 71,141 |
<p>I'm trying to do a little spatial analysis--just some simple spatial correlations. I have a data frame consisting of latitude and longitudinal points, a value to model, and a neighborhood indicator. To whit:</p>
<pre><code>d1 <- data.frame(long = runif(n=1000, 10, 10.1),
lat = runif(n=1000, 10, 10... | 32,458 |
<p>I am working on my thesis analysis, and I have some error data that's right-skewed. I log-transformed it and ran glm on it (gaussian, identity in R) weighted by sample size, and my data is still over-dispersed. I keep seeing comments about using the quasi family, but I'm not sure I completely understand what I'm doi... | 71,142 |
<p>From Tsay's Financial Time Series, there is a SARIMA model:
<img src="http://i.stack.imgur.com/UXVi5.png" alt="enter image description here"></p>
<p>He said that:</p>
<p><img src="http://i.stack.imgur.com/CFok9.png" alt="enter image description here"></p>
<p>I can't understand</p>
<ul>
<li><p>why deterministic s... | 71,143 |
<p>I have to generate a homogeneous Gaussian Field with given correlation function of each points on a three dimension grid (500 x 500 x 500). A Cholesky decomposition method fails because of huge number of points so I need to find another method. Could you suggest me the best way to generation this Gaussian Field?</p>... | 71,144 |
<p>I work in marketing, frequently running A/B tests on websites to determine which variation is best to serve to site visitors. I would like to be able to run a simulation that highlights the perils of repeated statistical significance tests (rather than a single significance test once sample size is met).</p>
<p>I'm... | 18,359 |
<p>The only difference I can think of is</p>
<p>Normal dist is defined on all values (negative, zero, positive), and is symmetric</p>
<p>Gamma dist is defined on positive values only, and is skewed to the right.</p>
<p>Similarity wise, they both are continuous distribution.</p>
<p>Anything else am I missing?</p>
<... | 71,145 |
<p>I have a dataset for vehicles and trying to predict what will fail. Here is my data set</p>
<pre><code>vId, MileageSincePartLastReplaced, AgeOfPart, TypeOfVehicle, Failure
x,100000,200days,Truck,Alt Belt
y,200000,600days,PCar,Transmission Belt
z,140000,230days,Van,Fan Belt
</code></pre>
<p>Failure is outcome v... | 49,863 |
<p>I'm using the arima method of stats package of R with my time series of 17376 elements. My goal is to get the value of the AIC criterion, I 've observed in my first test this:</p>
<pre><code> ts <- arima(serie[,1], order = c(2,1,1), seasonal = list(order=c(2,0,1),period = 24),
method = "CSS", optim.met... | 71,146 |
<p>I was wondering if it would make sense to calculate IRR for OLS (not poisson), but the OLS is done using log-transformed data?
I have a set of crude death rate data (which I'm still debating whether they are count data (because they are, after all, based on counts) or continuous data (since they are not integers), ... | 71,147 |
<p>Please consider the following graph</p>
<pre><code>library(igraph)
# Create random graph
vertices <- 100
g <- random.graph.game(vertices, .05, directed=FALSE)
# Assign attribute 1 to vertices
V(g)$attribute1 <- sample(1:100, vertices, replace=T)
# Assign attribute 2 to vertices
V(g)$attribute2 <- sa... | 71,148 |
<p>According to my knowledge, if input is provided as input,output pair then it is supervised learning. Only input is provided it is unsupervised learning.</p>
<p>load digit0; digitdata = [digitdata; D]; targets = [targets; repmat([1 0 0 0 0 0 0 0 0 0], size(D,1), 1)];</p>
<p>Here digit 0 image is provided as input ... | 71,149 |
<p>As described in a few of my previous questions (<a href="http://stats.stackexchange.com/q/3207/1381">here</a> and <a href="http://stats.stackexchange.com/q/2917/1381">there</a>), I am interested in deriving summary statistics from statistics reported in the literature.</p>
<p>I would very much appreciate any advice... | 71,150 |
<p>Or more specifically, why would the index of a dataframe not be in ascending numerical order?</p>
<p>When I display the dataframe, the first row has column names, the data begins on second row, but the leftmost column (which doesn't have a header), is not in order, instead it shows as:</p>
<p>2<br>
1<br>
4<br>
6<b... | 71,151 |
<p>I want to run a discriminant analysis on different motion capture measures to see which of the measures distinguishes best between my two conditions. The problem is that some of the standardized discriminant function coefficients are >1 and <-1. How is that possible? What did I do wrong? I used z-transformed data... | 18,623 |
<p>Consider the following graph:</p>
<pre><code>x <- 1:100
y1 <- rnorm(100)
y2 <- rnorm(100)+100
par(mar=c(5,5,5,5))
plot(x,y1,pch=0,type="b",col="red",yaxt="n",ylim=c(-8,2),ylab="")
axis(side=2, at=c(-2,0,2))
mtext("red line", side = 2, line=2.5, at=0)
par(new=T)
plot(x,y2,pch=1,type="b",col="blue",yaxt="... | 71,152 |
<p>I'm trying to compile a list of clustering algorithms that are:</p>
<ol>
<li>Implemented in R</li>
<li>Operate on sparse <em>data matrices</em> (not (dis)similarity matrices), such as those created by the <a href="http://www.rdocumentation.org/packages/Matrix/functions/sparseMatrix" rel="nofollow">sparseMatrix</a> ... | 24,478 |
<p>The goal is to design a variable to use in logistic regression which measures the importance of starting with possession of the ball in football. <code>Possession</code> is naturally a categorical variable, either the favored team has it, or it does not. However, after doing some research, it is clear that possess... | 32,462 |
<p>I am computing multivariate kernel density estimations on subsets of data in MATLAB. I have successfully done the KDEs with 47 different datasets of 45 points (each has an X and Y coordinate). But when I use small subsets, such as 7 or 8 points (again, each has an X and Y coordinate) I am getting an error that the c... | 71,153 |
<p>I am studying the article <a href="http://www.bmj.com/content/347/bmj.f7387" rel="nofollow">Barcelona baby boom: does sporting success affect
birth rate?</a>.</p>
<p>They are using month-data for their analysis of birth.
They have normalised one month to be 30 days.
So they have somehow cut values from one month to... | 71,154 |
<p>I have a variable that is measured using a 13-item, 4-point Likert scale with the exception of one item (yes $=1$, no $=2)$.</p>
<p>How can I calculate the total score for this variable?</p> | 49,864 |
<p>I am relating age to a binary outcome in a logistic model (or, more to the point I would like to). However, the distribution of the ages looks like this:</p>
<pre><code>nn <- 1000
age <- c(rpois(nn / 3, lambda = 0.5),
rnorm(nn / 3, mean = 10, sd = 2),
runif(nn / 3, min = 0, max = 15))
age <-... | 71,155 |
<p>Usually, when we do prediction algorithms we are happy obtaining a specific classification rate on a population. My question is: Is there any way of extending that result to wider populations? In other words, if I obtain a 89% of successful classification rate on 1000 individuals, what can I say about the performanc... | 71,156 |
<p>I'm using <a href="http://cran.r-project.org/web/packages/kernlab/index.html" rel="nofollow">kernlab package</a></p>
<p>Here are two examples:<br/>
First:</p>
<pre><code>library(kernlab)
x <- runif(1020, 1, 5000)
y <- sqrt(x)
model.vanilla <- rvm(x, y, kernel='vanilladot')
</code></pre>
<p>Got error:</p>... | 71,157 |
<p>Let's say I have an histogram of some continuous data with unknown and arbitrary pdf. I don't have access to the original raw data. So I don't know that 3 of my data points are 21, 25 and 27, all I know is that 3 of my data points are in the bin 20-30. How accurate is it to compute the moments of this pdf from the b... | 49,770 |
<p>I am doing an MSc in occupational therapy, which is concerned with evaluating how effective an occupational therapy intervention is on increasing individual's with learning disabilities daily living skills. I am working with a very small sample (5 to 8 people) and was planning on using a non-standardised assessment ... | 71,158 |
<p>I am having some issues interpreting the output of the <code>glm</code> model I am using for an eQTL analysis (an analysis of genotype vs. gene expression for a particular gene).
My model is as follows:</p>
<pre><code>fit <- glm(Expression ~ genotype + prep.no + sex, family = poisson, data = data)
</code></pre>... | 71,159 |
<p>It is easy enough to detect interdependence of two discrete-time white noise sequences - one just takes cross-covariance and compares it with variance. But what if both time series are "non-white", that is, there's long-range autocorrelation (like two Brownian random walks)? I assume one resorts to some kind of whit... | 71,160 |
<p>I have a toy example reproduced below in which the response variable has three possible classes. I am trying to create an ROC but not sure how to deal with it when there are three classes. Any help will be appreciated.
Thanks </p>
<pre><code>library(ipred)
control = rpart.control(maxdepth = 20, minsplit = 20, cp =... | 49,854 |
<p>This is a simplification of question: <a href="http://stats.stackexchange.com/questions/71448/how-many-users-will-connect-to-my-server">How many users will connect to my Server?</a>, in which I'm trying to make it simpler and more defined.</p>
<p>I have 5 days in a week.
Each day has 6 temporal slots of 1 hour.</p>... | 71,161 |
<p>I want to predict a categorical variable using also categorical predictors. Currently, I am looking at classification and regression trees (CART).</p>
<p>The prediction quality is "good enough", except for the presence of impossible combinations. In the following minimal example, the combination <code>a==2, b==2</c... | 18,368 |
<p>I am using the <a href="http://www.mathworks.fr/fr/help/stats/svmtrain.html" rel="nofollow">SVMStruct</a> function in MATLAB (with RBF kernel) to classify my data, and it works great. But now I need to compare the distance from the data points to the hyperplane, or to find the data point that is closest to the hyper... | 71,162 |
<p>SPSS Help provides the following help for testing group differences in a correlation, using the GLM approach. See <a href="http://www-01.ibm.com/support/docview.wss?uid=swg21478950" rel="nofollow">link</a>.</p>
<p>It first requires that X and Y are transformed into z scores.</p>
<p><strong>Question:</strong> When ... | 71,163 |
<p>I have a problem, which I think should be very common, but I mostly have been taught stochastic at university and most of my statistics knowledge is self-taught. Hence I have no clue on how to look for this on google or other search engines.</p>
<p>The basic question is, if I am testing a hypothesis against the nul... | 43,296 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/665/whats-the-difference-between-probability-and-statistics">What's the difference between probability and statistics?</a> </p>
</blockquote>
<p>Today I just came back from a student seminar in our dep... | 49,865 |
<p>I was just wondering why regression problems are called "regression" problems. What is the story behind the name? </p>
<blockquote>
<p>One definition for regression:
"Relapse to a less perfect or
developed state."</p>
</blockquote> | 32,485 |
<p>I have conducted a search for genetic interactions using a simple dosage model:</p>
<p>Y ~ A + B + AB</p>
<p>where Y is the phenotype, in this case, gene expression values and A and B are vectors of genotype information for ~500 samples. I wish to determine a signficance threshold using permutation testing in orde... | 43,305 |
<p>I've received a results from a Mann-Whitney rank test that I don't understand.
The median of the 2 populations is identical (6.9). The uppper and lower quantiles of each population are:</p>
<ol>
<li>6.64 & 7.2</li>
<li>6.60 & 7.1</li>
</ol>
<p>The p-value resulting from the test comparing these population... | 46,579 |
<p>I`m using IBM synthetic data generator to produce a transactional dataset, but i have some problems with the support of the item.</p>
<p>Example:</p>
<p><em>C:\ >"IBM Quest Data Generator.exe" lit -ascii -ntrans 10 -corr 0.75 -nitems 1 > output.txt</em></p>
<p>In this example I expected a data set with approximat... | 32,486 |
<p>I have a dataset and I would like to see how the dataset is organized via a hierarchy.</p>
<p>I have thought of using a divisive method as follows:</p>
<pre><code>1. Cluster the data into 2 classes using K-means (k=2)
2. Cluster Each of the 2 classes using K-means (with k=2) to create a total of 4 classes
3. And s... | 71,164 |
<p>I'm an almost graduated applied math student. I do some sporadic work in marketing. I have done a few market segmentation projects. I am soon going to do one which is important to me. I usually segment customer types: in a questionnaire people are asked about how they "feel" or what they "like" or consider "importan... | 43,311 |
<blockquote>
<p>Given is that all the assumptions for a linear regression $y_i=x_i'\beta + \epsilon_i$ hold for $i=1,\dots, n$. For the (n+1)st observation we can write: $y_{n+1}=x'_{n+1} \beta + \nu + \epsilon_{n+1} $Then prove that the Least Squares Estimator (LSE) for $\beta$ for the full sample is $b \ (=(X'X)^{-... | 71,165 |
<p>I have been working on an inverse regression addon for SPSS and using this paper heavily:
<a href="http://ge.tt/9l1m1iI/v/0" rel="nofollow">I. Lavagnini, F. Magno, A statistical overview on univariate calibration, inverse regression, and detection limits: Application to gas chromatography/mass spectrometry technique... | 71,166 |
<p>My question may be very basic but I hope that you can help me.
I have got two groups (A and B). I am measuring two continuous biological measures (X and Y) which are significantly positively correlated. Theoretically it is clear that X can influence Y but not vice versa.
Y has been measured two times (Y1 and Y2) and... | 71,167 |
<p>Say I have a feature matrix $X$ and a target $y$. I use $k$-fold cross validation to generate $k$ out-of-sample MSE curves as a function of a penalty parameter $\lambda$</p>
<p>$$MSE_i(\lambda) \quad (i=1,\dots,k)$$</p>
<p>Given these curves, how should I choose $\lambda$? Two approaches I have seen are</p>
<ol>
... | 71,168 |
<p>Given a non-normal distribution (a table) and a specific sample, how do I find the $MLE$ of the mean using the given sample?</p>
<p>To be more specific I was given the following distribution:</p>
<p>$$
\begin{array}{|c|c|c|c|}
\hline
\text{Number of Weeks} & 1 & 2 & 3 \\ \hline
Prob... | 71,169 |
<p><strong>I want the mathematical formula the statistical programs are using to compute alpha and beta.</strong>
I typically use G-Power to estimate the necessary sample size for a given power (1-beta) for an a-priori analysis.
The input it requires for this calculation is:
Type of analysis (t-test, difference betwee... | 32,499 |
<p>I use SPSS Clementine. I need to give a weight to one of my features to be considered much more than others as it is more important.
I can't find any option to do this for training a C5 tree.
the only option I saw is weightening some records, and not the attributes.</p>
<p>does any one know how can I do it?</p>
<... | 32,500 |
<p>I have many time series(retail data). Some with trends, some seasonal,
and some with neither. With period day, week or month. I need to make forecast, for each time serie. </p>
<p>I'm looking for the most efficient methods for forecasting in R ?
Which significant things should I know for it?
Maybe someone has exp... | 71,170 |
<p>I have a small sample unbalanced RCBD, where I have reason to suspect unequal variances, hence I wish to fit a ANOVA with type-3 SS with heterscedasticity consistent esimators. The simplest way to do this is to utilize Anova() function from the package CAR, however, I cannot for the life of me understand how to run ... | 32,501 |
<p>I am trying to build a model with 15 independent variables. However, because the parameters have been showing collinearity, I have been advised to use the Principal Component regression method. However, I am not sure how to calculate the principal components that can be used an inputs in regression. I am currently u... | 71,171 |
<p>How do I test the significance of cross-correlation values in SPSS? It seems there is no option for this.</p> | 32,504 |
<p>Is there a canonical/recommended approach to or algorithm for splitting up an interval with the intent of minimizing the number of segments while keeping a high accuracy? It is essentially an optimization problem and one possible solution would be to apply classification trees as I describe below. But this is a typi... | 32,505 |
<p><strong>Major edit: I would like to say big thanks to Dave & Nick so far for their responses. The good news is that I got the loop to work (principle borrowed from Prof. Hydnman's post on batch forecasting).
To consolidate the outstanding queries:</strong></p>
<p><strong>a) How do I increase the maximum number ... | 71,172 |
<p>I was following this wiki <a href="http://en.wikipedia.org/wiki/Kriging">article</a> related to ordinary kriging</p>
<p><img src="http://i.stack.imgur.com/UFQMB.png" alt="enter image description here"></p>
<p>Now my covariance matrix looks like this, for 4 variables</p>
<pre><code>1 0.740818220681718 0.548811... | 32,506 |
<p>I don't know how to denormalize (0-1 normalized) data after prediction. I have 1 output and several input values. It's clear for 1 input I must use min and max value previously used for normalization. </p>
<p>But what should I do if for normalizing, each input was normalized separately, using its own min and max va... | 71,173 |
<p>Suppose that I have a great algo for calculating the SVD and I want to do Kernel PCA.
It is possible to first apply the Kernel function to my data and then run the SVD algo on the transformed data?</p> | 32,519 |
<p>I'm working here on my research proposal for my alma mattera. I'm in accountancy science field, however, I need to deal with some statistics on this occassion. Would be very grateful if you could help me.</p>
<p>I have an idea to built this kind of regression model:</p>
<p>Y= x1 + x2 + x3</p>
<p>The research ques... | 71,174 |
<p>I am trying to understand the meaning of the "skewedness" parameter for scikit-learn's SkewedChi2Sampler and figure out how this value affects the output of the sampler. </p>
<p>I have looked at the docs <a href="http://scikit-learn.org/stable/modules/generated/sklearn.kernel_approximation.SkewedChi2Sampler.html#sk... | 32,520 |
<p>How can I derive the distribution of $$\bar{X^2}\quad \text{when}\quad X\sim N \left( \theta, \sigma^2 \right) $$</p>
<p>The context of this question is an exercise requiring me to show that $\bar{X^2}- \frac{\sigma^2}{n} $ is an unbiased estimator of $\theta^2$ and afterwards find its efficiency. Thus I must find... | 71,175 |
<p>In the dark ages, we would map the results of a Student's t-test to a null hypothesis probability <em>p</em> by looking up <em>T</em> and degrees of freedom in a table to get an approximate result. </p>
<p>What is the mathematical algorithm that generates that table? <em>ie</em>, how can I write a function to gener... | 18,378 |
<p>The transfer entropy, from information theory, is an effective way to measure the one-way information dependence between two variables. A nice high-level summary is here:
<a href="http://lizier.me/joseph/presentations/20060503-Schreiber-MeasuringInfoTransfer.pdf" rel="nofollow">http://lizier.me/joseph/presentations/... | 71,176 |
<p>I'm looking for a large dataset (~20k nodes,~100k edges) for a geometric network, like utility networks, etc (<a href="http://gis.stackexchange.com/questions/6885/difference-between-network-dataset-and-geometric-network">See</a>)</p>
<p>Ideally, at a minimum I would like a dataset that includes identified 'nodes' ... | 32,528 |
<p>First off, let me say that I'm extremely poorly versed in statistics, and this is a question purely about terminology.</p>
<p>I have a distribution for some quantity (height of person, say) and the most likely 95% of outcomes are within some range $h_0$ to $h_1$. I want to know what to call (ideally a 2 or 3 word p... | 71,177 |
<p>Here i am again. From this script:</p>
<pre><code>model1 <- zelig(Decision ~ as.factor(age) + as.factor(income) + as.factor(town.type) +
tag(town.type|town), model="logit.mixed", data=Fish)
</code></pre>
<p>Does it mean that <code>town.type</code> is treated both as fixed effects and random effe... | 71,178 |
<p>I am trying to make a custom Neural network structure using 'network' command.</p>
<p>I am a little confused.Can we change the connections between individual neurons?Like it is possible in weka?</p> | 71,179 |
<p>Has learning theory ever been applied in practice for search log data? If so, what are some findings about generalization/learnability from this data?</p>
<p>I'm interested in generalization about an individual user's search behavior from a time slice or generalization about a total population of users, given a sa... | 32,529 |
<p>I'm trying to create a second order polynomial fit to some data I have. Let's say I plot this fit with <code>ggplot()</code>:</p>
<pre><code>ggplot(data, aes(foo, bar)) + geom_point() +
geom_smooth(method = "lm", formula = y ~ poly(x, 2))
</code></pre>
<p>I get:</p>
<p><img src="http://i.stack.imgur.com/t... | 71,180 |
<p>Disclaimer: I do not have a background in statistics or the math behind filtering, save one long-time-ago college course.</p>
<p>I have a well defined problem space. I am calculating hourly staffing requirements for retail stores. </p>
<p>The raw values are based on a matrix of the full-time employees required for... | 71,181 |
<p>I have two questions about Bonferroni adjustments:</p>
<p>1). Can one use the Bonferroni method to compare independent groups? The reason why I ask this is it seems that many examples I've encountered discuss the Bonferroni method in the context of comparing dependent groups - for example, multiple comparisons afte... | 71,182 |
<p>For a <a href="http://en.wikipedia.org/wiki/Likelihood-ratio_test" rel="nofollow">likelihood-ratio test</a> (LRT) statistic, $\Lambda(x)$, the asymptotic distribution of the statistic $-2 \log \Lambda(x)$ is a chi-squared distribution, which occurs only under certain regularity conditions. Here, we have two hypothes... | 71,183 |
<p>I'm wondering if I've violated the assumption of independence in a generalised linear model. The data I've used to make to make the model can be downloaded with this code:</p>
<pre><code>library(repmis)
goose_feeding <- repmis::source_DropboxData("goose_feeding.csv", "gz6v6hvjytqn14n", sep = ",", header = TRUE)
... | 71,184 |
<p>I recently stumbled upon the concept of <a href="http://www.google.com/search?q=%22sample%20complexity%22" rel="nofollow"><strong>sample complexity</strong></a>, and was wondering if there are any texts, papers or tutorials that provide:</p>
<ol>
<li>An introduction to the concept (rigorous or informal)</li>
<li>An... | 43,355 |
<p>I'm comparing samples of remote sensing data points collected over two different areas, so basically I come up with a pair of data set and I run the same analysis on both of them.
Comparing the linear models (t-test) I found that the slopes and intercepts are significantly different from each other.
Nonetheless, sin... | 71,185 |
<p>If I multiply the two PDFs, does the variance of the result PDF becomes narrower than the two PDFs always?
In other words, if I multiply likelihood and prior to get the posterior, is the variance of the posterior narrower than that of the likelihood and prior?</p>
<p>Thanks</p> | 71,186 |
<p>Given two histograms, how do we assess whether they are similar or not?</p>
<p>Is it sufficient to simply look at the two histograms?
The simple one to one mapping has the problem that if a histogram is slightly different and slightly shifted then we'll not get the desired result.</p>
<p>Any suggestions?</p> | 71,187 |
<p>I would like to compare whether or not the correlation between 2 variables are the same in 2 experimental groups, each with 6 replicates. The two variables that I would like to compare are non-normally distributed. For each replicate, I have ~100-150 measurements of both variables and a total sample size of around... | 71,188 |
<p>I know that a Type II error is where H1 is true, but H0 is not rejected. </p>
<h3>Question</h3>
<p>How do I calculate the probability of a Type II error involving a normal distribution, where the standard deviation is known?</p> | 71,189 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/8107/how-do-i-interpret-the-results-of-a-breuschpagan-test">How do I interpret the results of a Breusch–Pagan test?</a> </p>
</blockquote>
<p>how I can interpret the results of these two tests for heterosk... | 49,866 |
<p>I have a logistic regression model with several categorical explanatory variables and one interaction term (between two binary variables, named A and B). I know how to calculate the odds ratios for the different levels of A and B (for A=1, e.g., I need to add the coeff for A and coeff for A*B, then exponentiate), bu... | 32,535 |
<p>I found <code>auto.arima()</code> function in <code>forecast</code> packages.
As far I have understand how it works, It should find the best model for the data, my question is: Is it possible to understand if the variance is not constant during all the period(timeseries) using that function? I mean...
If it fit a mo... | 71,190 |
<p>I am trying to learn how to apply unsupervised classification to spatial data.
In near infra red satelite pictures; the ocean is dark and the forest is white.
Each pixel in such an image is an observation. I guess the variables are [x-position, y-position, grayscale]?</p>
<p>Which methods could I use to classify th... | 71,191 |
<p>I am working on a machine control project. We can measure the motor's current during operation. Sample data from two motors performing an operation successfully is below. The red trace shows the current from one motor, the blue trace the current from another. I'd like to try and come up with an algorithm for ide... | 32,541 |
<p>I'm trying to label a pretty simple scatterplot in R. This is what I use:</p>
<pre><code>plot(SI, TI)
text(SI, TI, Name, pos=4, cex=0.7)
</code></pre>
<p>The result is mediocre, as you can see (click to enlarge):</p>
<p><a href="http://i.stack.imgur.com/stAuk.png"><img src="http://i.stack.imgur.com/stAuk.png" alt... | 71,192 |
<p>Are there any multi-variate continuous distributions whose probability distribution functions give high values for sparse vectors and low values for dense vectors, i. e. indicating the sparseness of the vector?</p>
<p>I found one sparseness measure in [1] which is as follows for $x \in \mathbb{R}^n$:</p>
<p>$$s(x)... | 8,170 |
<p>I'm trying to reduce dataset dimensionality. PCA is a good metric but that gives me new dataset. My goal is to determine from number of events (e.g. 60) and number of trials (e.g. 6) which events are more relevant. </p>
<p>For example:</p>
<ul>
<li>1st, 3rd, 21st, 45th ... (N total) events are good enough to appr... | 71,193 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.