question stringlengths 37 38.8k | group_id int64 0 74.5k |
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<p>I am studying a machine learning course and the lecture slides contain information what I find contradicting with the recommended book.</p>
<p>The problem is the following: there are three classifiers:</p>
<ul>
<li><strong>classifier A</strong> providing better performance in the lower range of the thresholds,</li... | 72,278 |
<p>Suppose I have three different models $M_1, M_2$ and $M_3$, these models are nested such that $M_1 \subseteq M_2 \subseteq M_3$. I perform two likelihood ratio tests, $M_1$ against $M_3$ and $M_2$ against $M_3$. In this case how do you control the familywise error rate (feel free to imagine that there is a long chai... | 30,778 |
<p>I have a sample (n=200) that I have collected questionnaire data from. Each participant will complete 5 questionnaires that capture different behaviours and all of my 5 questionnaires include between 10 and 27 items. </p>
<p>I am planning to use SEM to construct a model that investigates whether scores on 4 of my q... | 37,978 |
<p>There is a population $D$ in which each data point has two attributes $X$ and $Y$ that are randomly distributed. While they are probably not exactly normally distributed I imagine they are not too pathological. I don't know their means and $s.d.$'s, but they are likely to be somewhat similar. I also don't know a pri... | 72,279 |
<p>The life time of a bulb follows exponential distribution. Such types of examples frequently occurs in many areas of science and engineering. Is there any source of practical data set of two exponential distributed data with a location and scale parameter? </p> | 34,139 |
<p>I'm modelling propensity to purchase a particular product or service following exposure to online advertising.</p>
<p>I'm attempting to get something like the analysis from John Chandler-Peplnjak's thesis <a href="http://etd.lib.umt.edu/theses/available/etd-07082010-093812/unrestricted/ChandlerPepelnjak_umt_0136D_1... | 72,280 |
<p>I have 4 groups, 3 of them receiving a treatment and the last nothing. I will do two mesures, before and after the treatment. But my groups are pre-defined, not resulting of a random selection. </p>
<p>Is it nonetheless valid to use an ANOVA with repeated mesures ?</p>
<p>Thank's beforehand </p> | 72,281 |
<p>I often come across that, in Bayesian inference, to encourage sparseness, we should choose a heavy-tailed probability distribution as prior.</p>
<p>AFAIK, in heavy-tailed distribution, it's more likely for a random variable to take on large or extreme values. </p>
<p>Now for a multivariate random variable $\bf{x}$... | 72,282 |
<p>I'm trying to determine which type of learning algorithm is best for making predictions on my data. My data set consists of several independent variables, each of which is accompanied by an "indicator" variable that represents the sample size used to acquire its specific value.</p>
<p>Let's say I'm attempting to as... | 72,283 |
<p>One of the <a href="http://en.wikipedia.org/wiki/Student%27s_t-test#Assumptions" rel="nofollow">assumptions</a> for t-tests is that the data must follow a normal distribution.</p>
<p>However, due to the <a href="http://en.wikipedia.org/wiki/Central_limit_theorem" rel="nofollow">Central Limit Theorem</a> (and <a hre... | 72,284 |
<p>I am trying to model my data with ARIMA(1,2,12) and since the variance is not stationary I have also included GARCH (2,3). I have saved all the parameter of my model in a variable called mdl. I have used 1000 time steps as initial values and I want to do a 10 time step ahead for forecasting and then I want to comput... | 6,493 |
<p>I am trying to perform a power calculation using G*Power. I need $\eta_P^2$, but the ez package for R gives me $\eta_G^2$. I understand the reasons for it doing this, but I still need $\eta_P^2$ for a power calculation for a replication. Is there a way that I can calculate $\eta_P^2$ from the ezANOVA output, or conv... | 72,285 |
<p>Background - I want to cluster analyze a mixed dataset, clustering the variables on the basis of correlational similarity. SPSS gives me this option, but doesn't allow me to evaluate the clustering solutions by providing statistical measures of heterogeneity change (e.g. pseudo F statistic) or direct measures of het... | 72,286 |
<p>I am investigating patterns in click-order on images. A user is asked to click on an image in 5 places (can be the same place). This sequence of 5 clicks makes up a graphical password. I am looking for patterns in the order in which users click e.g. they scan from left to right i.e. x_1 < x_2 < x_3 < x_4 &l... | 34,144 |
<p>I have sales data and would like to see if the median sales for an employee has increased as a result of this training. Thus, I have pre and post data, since it is only six months and am interested in the median difference I plan to use the Wilcoxon signed rank. When performing this analysis I took the difference of... | 34,145 |
<p>I know that the PDF is the first derivative of the CDF for a continuous random variable, and the difference for a discrete random variable. However, I would like to know why this is, why are there two different cases for discrete and continuous?</p> | 34,146 |
<p>Suppose we have $N_A$ and $N_B$ samples from population A and B respectively. For each sample, we have his/her weight and height. What interests us is whether there are a significant difference in weight between A and B. A <em>t</em>-test can do this easily. But we also know there is strong correlation between heigh... | 72,287 |
<p>I've just started look into recurrent neural network. I found three sources of information on Elman's network(Elman 1991).</p>
<p>(Example and code) <a href="http://mnemstudio.org/neural-networks-elman.htm" rel="nofollow">http://mnemstudio.org/neural-networks-elman.htm</a></p>
<p>(Paper) <a href="http://www.sysc.p... | 72,288 |
<p>Following the question <a href="http://stats.stackexchange.com/questions/18403/significant-interaction-in-linear-model-with-pearson-r-as-possible-explanation">here</a>, someone suggested that I could just look at the B column in SPSS "Parameter Estimates" table to interpret the interaction.</p>
<p>For instance, the... | 34,149 |
<p>Is there an implementation of n-gram smoothing like Kneser-Ney in R?</p>
<p>I'm using the <code>tm</code> package.</p> | 17,498 |
<p>I am trying to fit a predictive gene-based model in survival analysis. My question is:</p>
<p><strong>Can I use LASSO as a variable selection method, and then run a multivariate Cox regression to get the coefficients of those variables (genes) instead of using the coefficients from LASSO?</strong></p>
<p>In that c... | 72,289 |
<p>I have a sample size of $21$ with $496$ observations.Can I presume an approximately normal distribution,and use a $t$-test to compare the difference in means, and difference in various financial features (Financial data daily prices)? </p>
<p>In addition, sometimes I get insignificant differences on the daily basis... | 72,290 |
<p>I am a grad student developing an interest for statistics. I like the material over-all, but I sometimes have a hard time thinking about applications to real life. Specifically, my question is about commonly used statistical distributions (normal - beta- gamma etc.). I guess for some cases I get the particular prope... | 72,291 |
<p>Is it possible to simulate two time series AR(1) for example 0.5 and 0.8 and at the same time these time series to be correlated with $\rho = 0.8$ using R?</p>
<pre><code>ts.sim <- arima.sim(list(order = c(1,0,0), ar = 0.9), n = 100)
ts.sim2 <- arima.sim(n = 100, list(ar=c(0.9)),n.start = 25)
et<-rnorm(100... | 72,292 |
<p>I was going through some tutorials on information theory. It had the following example concerning transmission of three symbols $A, B$ and $C$ such that
$P(A) = 1/3 = P(B) = P(C)$</p>
<p>If we encode the events as $A = 0, B = 10, C = 11$ ; then we get on an average $1.66$ bits per symbol. But it mentioned that the... | 72,293 |
<p>I have some species $\times$ year matrices and analyse the temporal dynamics by regressing distance between years on $\sqrt{ {\rm time \ lag} }$. Since the data points are not independent and since I get $(n^2-n)/2$ distances for a time series of length $n$, it's problematic to use the standard way of determining th... | 72,294 |
<p>First of all, I am very new to this subject. I have been using weka some days to familiarize myself and reading about data mining to understand it.</p>
<p>I have a dataset (from UCI, <a href="http://archive.ics.uci.edu/ml/datasets/Statlog+%28German+Credit+Data%29" rel="nofollow" title="this one">german credit data<... | 34,153 |
<p>I'm trying to understand how polynomial kernel functions work, in my textbook it shows an example with a degree of 2, with an input dimension of 2:</p>
<p>$K(\vec{x}, \vec{y})$ = $(1 + x_1y_1 + x_2y_2)^2$</p>
<p>= $1 + 2x_1y_1 + 2x_2y_2 + x^2_1y^2_1 + 2x_1x_2y_1y_2 + x^2_2y^2_2$</p>
<p>I understand all of the abo... | 34,154 |
<p>I want to compare two exchange rate models namely Balassa-Samuelson model and monetary model of exchange rate. Both models are totally different from each other and their dependent variables are also different. I don't know how to compare these two models and which econometric technique I should use for this compari... | 72,295 |
<p>My task is to show that Fisher's criterion distribution when the null hypothesis is true follows $F(k-m,N-k)$ when df increases. Here $k-m$ is number of restriction.</p>
<p>So I can write a null hypothesis H0: $b_1=b_2=\ldots b_k=0$.<br>
And I think that I can show that F-statistic follows $F(k-m,N-k)$ using restr... | 34,155 |
<p>I have 10 independent ordinal variables, each having 5 levels, all intended to measure the same latent construct, and one ordinal dependent variable named <code>rank</code> with 5 levels. I have read somewhere that for using regression, it is necessary to convert categorical variables with multiple levels to dummy ... | 72,296 |
<blockquote>
<p><a href="http://math.stackexchange.com/questions/61460/calculate-expectation-from-empirical-cdf">Mirror thread on Math.SE</a></p>
</blockquote>
<p>I have a empirical cumulative probability distribution function for a random variable. The random variable is "time to failure" and I have the full curve ... | 45,224 |
<p>Suppose that a certain disease (D) has a prevalence of 3/1000. Also suppose that a certain symptom (S) has a prevalence (in the general population = people with that disease D and people without that disease [probably with other disease, but it's not important]) of 5/1000.
In a previous research, it was discovered t... | 72,297 |
<p>When conducting a factor analysis, we need to check the normality and constant variance assumption of the original variables.<br>
If there is HSK existing in the data, can I do different transformations(for example log transformation to x1, squared x2...) to different variables and then conduct the analysis?<br>
Or ... | 34,157 |
<p>I have a sequence of two possible observations ($A$, $B$) and want to train an HMM with $h$ states, namely $\lambda_h$, to predict the probability of the next observation using the Baum-Welch algorithm. Output probability distributions are Bernoulli with parameter $p_i$ ($i$ is the state number). </p>
<p>My proble... | 72,298 |
<p>I have performed the path analysis using the <code>sem</code> function in R. The model which I fitted consists of both direct and indirect paths. I have some trouble in interpreting the estimates of the SEM coefficients. </p>
<ul>
<li>Does R gives the value of total effect = (direct effect + indirect effect) direct... | 72,299 |
<p>I'm trying to develop a non-linear model, but I'd like to have the values for the parameters vary by group. To give you an example, a section of my data (just random numbers here) looks like:</p>
<pre><code> MONTH FUTURE.PC FUTURE.SALES
1 APR 35 1498
2 APR 22 1124
3 MAY 2... | 72,300 |
<p>I've read these SO questions and this is not duplicate of them</p>
<ul>
<li><a href="http://stackoverflow.com/questions/1306785/best-way-to-statistically-detect-anomalies-in-data">best way to statistically detect anomalies in data</a></li>
<li><a href="http://stackoverflow.com/questions/3531374/statistical-calculat... | 34,159 |
<p>Im looking for a method that would allow me to estimate the value of 1 variable, described by 3 other variables.
I have a set of measurement data collected with my camera. Each record consists of:</p>
<ol>
<li><p>Pixel brightness (describing the ammount of infrared radiation emitated by a body during picture captur... | 17,543 |
<p><strong>EDIT</strong></p>
<ol>
<li><p>When we add noise to system we say it is white noise. White noise will have a constant power spectral density, flat power spectrum. But what is the advantage of this?</p></li>
<li><p>Why do we need iid property?</p></li>
<li><p>When we find out the probability density function ... | 72,301 |
<p>I'm trying to use central limit theorem to compute the mean of the sample, however the population where I'm sampling has value only between 0 and 1, can I use mean of the sample as mean of the population and standard error = (population's standard error / sqrt(n))?</p>
<p>I have done it, but the distribution does n... | 72,302 |
<p>I am wondering if I understand those terms correctly. To summarize my thoughts:</p>
<p>In naive Bayes, our decision rule is basically the Maximum a posteriori (MAP) estimate of our hypothesis. We assign an observation $\pmb x$ to the class $\omega_j$ that has the largest posterior probability:</p>
<p>\begin{equati... | 72,303 |
<p>How do i design the use of Multiple Imputation based on Bayesian Inference when I am dealing with categorical data and my dataset does not contain complete prior observations at every combination ? </p>
<p>For example i have three categorical variables </p>
<pre><code> x1, x2, x3,
x1 {1,2,3}
x2 {1,2}
x3 {1... | 72,304 |
<p><img src="http://i.stack.imgur.com/zAuqM.jpg" alt="enter image description here">In my regression model of BMR on age (yrs) , gender (1=male, 0=female), height and weight. The regression equation obtained is:</p>
<p>BMR = 1232.059+13.281 weight+3.954 age+192.214 male-3.471 age:gender.</p>
<p>Please interpret the n... | 49,892 |
<p>I am currently working on a modification of a clustering algorithm to suit my problem domain. </p>
<p>I want to know which methods are available for me to compare the centroids generated from the two methods?</p>
<p>That is, <strong>I want to know how well my (modified) clustering method agrees with the current me... | 34,164 |
<p>I have been asked to produce a pie graph of some categorical data.</p>
<p>On a simple scale it look like this:</p>
<pre><code>House 1: Speak a foreign language , own a computer
House 2: Only lived in by women
House 3: Only lived in by women, speak a foreign language
House 4: Has pets
House 5: Has pets, own a compu... | 17,560 |
<p>I am new to statistics and would really appreciate help. The people within the groups are different - how do I compare the percentages to see if there is a statistical significance between the groups that had training and between the group that did not</p>
<p>It looks something like this:</p>
<pre><code>group 1 ... | 72,305 |
<p>I am looking to have People rate certain items on a scale of 0-10 based on those items perceived utility to the particular Person performing the rating. Fractional values are permitted. Giving no rating on an item is also permitted; however, I prefer to rank "highly rated" items with more ratings higher than "highly... | 30,787 |
<p>I have two prediction models. The first one returns answers in the range 0 to 1, where the correct answer is 0 or 1. The second returns answers in the range -1 to 1, and the correct answer is -1 or 1.</p>
<p>I have the MSE for both modes, and I want to compare performance.</p>
<p>What is the correct way to do this... | 72,306 |
<p>I encountered some problem while getting the
$\mathbb{E}[x]$ of a continuous random variable.<br>
The following equation is the PDF that im trying the expectation. </p>
<p>$\mathbb{E}[x] = \int_0^\infty x^2\alpha^2e^{-\alpha x}dx$ </p>
<p>I got stuck of how to get next step of<br>
$[-\alpha x^2e^{-\alpha x}]_0^... | 72,307 |
<p>I'm trying to answer a homework question and have found the following example online similar to what I need to accomplish for classifying unknown data in a decision tree. I don't quite understand why on slide 5 "Wind =String" is removed from the rule? I've read elsewhere that it's to do with removing information wit... | 72,308 |
<p><em>I asked <a href="http://www.biostars.org/post/show/48338/approximately-unbiased-bootstrap-vs-bootstrap/" rel="nofollow">this question at BioStar</a> but did not get a reply, so Im posting the question here.</em></p>
<p><strong>What is a simple explanation of what an approximately unbiased bootstrap is with rega... | 34,169 |
<p>Suppose we wish to test<br><br>$H_{0} : p = 0.5$ vs $H_{1} : p = p_{1}$ (where $p_{1} \gt 0.5$ <br><br>
What are the relative difficulties of testing for $p_{1}$ close to $0.5$ or $p_{1}$ far from $0.5$? <br><br>I know that the further $p_{1}$ is from $p_{0}$, the closer to one the power will be, and the further awa... | 72,309 |
<p>Related my earlier question <a href="http://stats.stackexchange.com/questions/31597/graphing-a-probability-curve-for-a-logit-model-with-multiple-predictors">here</a>. Having "mastered" linear regression, I'm trying to learn everything I can about logistic regression and am having issues turning largely "useless" coe... | 37,971 |
<p>I have a certain confusion while taking the derivative of the log likelihood of the conditional random field. As given in this paper <a href="http://people.cs.umass.edu/~mccallum/papers/crf-tutorial.pdf" rel="nofollow">http://people.cs.umass.edu/~mccallum/papers/crf-tutorial.pdf</a></p>
<p>I mean while calculating ... | 34,172 |
<p>I'm running a linear regression. The response variable is a proportion, and has quite a lot of zeros. The predictor variable is normal distributed. </p>
<p>My two variables look something like these:</p>
<pre><code>set.seed(50)
y <- sample(c(rep(0, 20), seq(0, 1, by=0.01)), 100)
set.seed(50)
x <- rnorm(100)
... | 72,310 |
<p>I have biological time series (9 years long) of the biomass of species which logically exhibit a seasonal pattern. I would like to cluster them into a few groups based on their typical seasonal evolution (e.g. spring vs. summer species).
To do so, I was advised to use Fourier transform in order to decompose their s... | 17,600 |
<p>The question is best illustrated by this example which uses a dataset (in library <code>faraway</code>) and <code>lme4</code> library (both in R). This intercept-only model is only for illustrative purposes.</p>
<pre><code>library(lme4)
library(faraway)
data(epilepsy)
log(mean(epilepsy$seizures))#expected intercep... | 72,311 |
<p>This is a very simple question posed to me by a friend of mine. I know it's a statistical analysis problem, but I suck at math.</p>
<p>Given the total population of $x$ within a metropolitan area, what would be the formula to determine approximately how many single heterosexual men or women there are between age($\... | 34,177 |
<p>I have a dataset that has budget numbers for various organizations. The numbers range from less than a million to hundreds of millions. The dataset also has information about various departments in the organization. For example it has the number of employees, the number of assets they maintain, etc. </p>
<p>I want ... | 34,179 |
<h2>Question:</h2>
<p>Is there a "rule of thumb" for choosing a False Discovery Rate threshold for accepting results when empirically estimating an FDR from repeated randomization of the original data set to abolish the "real" relationships?</p>
<h2>Example:</h2>
<p>Lets say that I have three linked data sets:</p>
... | 34,180 |
<p>I have a simple question for you, which has to do with style. Since I am a novice in writing research papers, I have the small issue of not knowing how to represent an equation in an acceptable way.</p>
<p>I am running an OLS regression, for which I use year fixed effects. Since I do not wish to write up every b*ye... | 72,312 |
<p>I was performing an experiment but got a higher validation accuracy than training accuracy. I've got a 39 mice data and performed leave one out cross-validation. The validation accuracy was 100%. But when I repeat the experiment on the whole training data (with optimal parameters selected by cv), the highest trainin... | 821 |
<p>I am developing a multi-class perceptron algorithm and was wondering if there are any datasets that could be used to test a multi-class perceptron? - A dataset where the classes are linearly separable and have at least 100 or more instances for training?</p> | 48,580 |
<p>In <a href="http://stats.stackexchange.com/questions/28730/does-it-make-sense-to-add-a-quadratic-term-but-not-the-linear-term-to-a-model/28741#28741">this answer</a>, under: "Why include the linear term?" in the answer, it mentions the relationship can be written two ways. Later it says that the point where $x=b$ is... | 72,313 |
<p>I have a simple Self organizing map that I have been working on. It has an output neuron for all 26 letters, and when I provide it with 26 samples (one for each letter) it quickly is trained to an error rate below 1%. It is fairly accurate, but when I want to add more samples, one for each output neuron, the lowes... | 72,314 |
<p>After doing a factor analysis, I decide to use that factor to test a hypothesis. However, I am not sure what data type of the Factor score the is (i.e., nominal , scale, etc.). Can I do a t-test or ANOVA as usual? </p> | 72,315 |
<p>I would like to obtain 95% confidence intervals for centroids based on Gower similarity between some mulivariate samples (community data from sediment cores). I have so far used the <code>vegan{}</code> package in R to obtain modified Gower similarity between cores (based on Anderson 2006; now included in R as part ... | 45,247 |
<p>I have an experiment that produces a few thousand data points which I then have repeated 5 times. Now I wonder how to calculate one single median to summarize all of them. </p>
<ol>
<li>I could combine the data from the five repetitions and calculate a median for that.</li>
<li>I could calculate a median for each e... | 898 |
<p>Can one define a pair of stochastic processes with independent alpha-stable increments and different alpha parameter (index of stability) values (e.g. a Brownian motion and a Cauchy or Levy process) which are correlated?</p> | 45,252 |
<p>When reading about how to approximate the distribution of the sample mean I came across the nonparametric bootstrap method. Apparently one can approximate the distribution of $\bar{X}_n-\mu$ by the distribution of $\bar{X}_n^*-\bar{X}_n$, where $\bar{X}_n^*$ denotes the sample mean of the bootstrap sample. </p>
<p>... | 72,316 |
<p>I tried to get a result in regression on <code>LIBSVM</code>, and I get the same problem on single feature data or multivariate data.</p>
<p>Suppose I try to find the price of something, and I have the data for $N$ days. I give the day ($1,2,\ldots,N-1$) price for $X$ as independent variables, and I train it with t... | 34,192 |
<p>I'm preparing for an exam and I came across this problem from old exams. I'm really clueless on how to solve it.</p>
<p>Consider a sequence of random variables $\{X_n\}_{n=1} ^\infty$ defined on the probability space $([0,1],B[0,1],\lambda)$ where $\lambda$ is Lebesgue measure. Define $X_n(\omega) = 1_{[1/2-(2n)^{... | 72,317 |
<p>There is a significant 3-way interaction in a data-set I'm working with.</p>
<p>The interaction involves both categorical and quantitative variables.</p>
<p>I have been pointed towards simple slopes and this <a href="http://www.jeremydawson.co.uk/slopes.htm" rel="nofollow">website</a> but I find the explanations l... | 34,193 |
<p>I have a data set that represents exponential decay. I would like to fit an exponential function $y = Be^{ax}$ to this data. I've tried log transforming the response variable and then using least squares to fit a line; using a generalized linear model with a log link function and a gamma distribution around the resp... | 147 |
<p>Two variables were known to me: <code>dark sample</code> and <code>light sample</code></p>
<p>To see if measured distance of sample components affected the shade of samples, I measured component distance of three dark samples and three light samples.</p>
<ul>
<li>I measured each sample three times - for repeatabil... | 72,318 |
<p>I hope this isn't a silly question, I'd like some advice on following up a threeway interaction in a mixed effects model. I've been building my models incrementally, like this:</p>
<pre><code>lmer0<- lmer(predval ~ 1 + (1 + Quantile|Subj), data = d)
lmer1<- update(lmer0, .~. + epoch)
lmer2<- update(lmer1, ... | 72,319 |
<p>K-fold cross-validation can be used to estimate the generalization capability of a given classifier. Can I (or should I) also compute a pooled variance from all validation runs in order to obtain a better estimate of its variance?</p>
<p>If not, why?</p>
<p>I have found papers which <a href="http://www-njv.slu.se/... | 72,320 |
<p>I would like to use a 5-item subscale to measure the effects of a behavioural intervention program on the use of behavioural strategies. I obtain significant results when I analyse it in models however the reliability of this measure is very low at .5 and the mean inter-item correlation is below .2. Can I use this m... | 72,321 |
<p>I am using $\chi^2$ to analyze a set of data gathered over 4 time periods. The two variables are independent--each 'event' is categorized as 'good' or 'bad'. We want to prove that the intervention caused an increase in the good events and decrease in the 'bad' events, or at least that the increase in good events out... | 72,322 |
<p>I was thinking about CI and subjective Bayesian and I have following two questions:</p>
<ol>
<li><p>If a subjective (<em>not objective</em>) Bayesian would care if her predictions don't do well in the real world.</p></li>
<li><p>A classical statistician would not care if her confidence statement is (obviously) wron... | 72,323 |
<p>Quantum Mechanics has generalized probability theory to negative/imaginary numbers, mostly to explain interference patterns, wave/particle duality and generally weird things like that. It can be seen more abstractly, however, as a noncommutative generalisation of Bayesian probability (quote from Terrence Tao). I'm c... | 34,199 |
<p>we have a process in which, at each step, a set of elements are presented to user, the user choses one, his choice is recorded and next round starts with a new set of elements.<br>
For example:<br>
1. {20,50,80} and the user chose 80<br>
2. {80,110,140} and the user chose 80 again<br>
3. ...</p>
<p>We want to verif... | 72,324 |
<p>On the <a href="http://en.wikipedia.org/wiki/Naive_Bayes_classifier#Testing">Wikipedia page about naive Bayes classifiers</a>, there is this line: </p>
<blockquote>
<p>$p(\mathrm{height}|\mathrm{male}) = 1.5789$ (A probability distribution over 1 is OK. It is the area under the bell curve that is equal to 1.) </p... | 49,345 |
<p>The <code>density()</code> function in <code>R</code> allows me to enter observations and get an empirical density that I can plot x and y values. I like it because it allows me to weight observations according to how important they are, and it allows me to specify the smoothing bandwidth I want.</p>
<p>My question... | 72,325 |
<p>I am attempting to use a neural network, after using other machine learning algorithms. I am using the <a href="http://cran.r-project.org/web/packages/RSNNS/index.html" rel="nofollow">RSNNS package</a> (I am willing to use / evaluate other packages) that's part of R. I would like to get a precision that's at least... | 34,200 |
<p>I have done the first part of the question already I just need help on the second part.</p>
<p>You read in a U.S Census Bureau that a 99% confidence interval for the mean income in 2005 of American households headed by a college educated person at least 25 years old was 100,272±1651. Based on this interval, can you... | 34,201 |
<p>I am doing a meta-analysis of observational studies. As the disease I am working on has different stages, some of the studies reported ORs (95%CI) for each stage separately in comparison to a single (shared) control population. I wonder if we can combine these two ORs (and their 95%CI) given that they reflect two ca... | 34,202 |
<p>I want to develop techniques for attribute selection (important independent variable X) using Partial least square 2 regression(PLS2R) for a large data sets .Initially i tried using multivariate linear regression using many independent variable (X) and many dependent variable (Y).So i got different regression mode... | 34,203 |
<p>I'm looking for the best way to test the hypothesis that two groups are different considering the relationship between two variables. </p>
<p>There is a population of individuals and, for each individual $x$, I know a value $m(x)$ from 0 to 100 and a binary value $s(x)$. I know there is a strong correlation betwee... | 72,326 |
<p>I've been rethinking an <a href="http://stats.stackexchange.com/a/104715/36229">answer</a> I gave to a question a couple weeks ago</p>
<p>Hold-out cross-validation produces a single test set that can be used repeatedly for demonstration. We all seem to agree that this is in many ways a negative feature, since the o... | 72,327 |
<p>I have the following matrix:</p>
<pre><code> category
I II III
1 70 300 5
word 2 20 400 45
3 10 300 0
</code></pre>
<p>It shows the number of times that a word_i appears in a phrase of category j, for example, word_1... | 72,328 |
<p>I have the following dataset:</p>
<pre><code>OXXO
</code></pre>
<p>The output of classification method #1 is:</p>
<pre><code>OOXO
</code></pre>
<p>Classification method #2 has a prediction confidence estimator and it's output is:</p>
<pre><code>O~X~
</code></pre>
<p>where ~ indicates that method #2 refuses to ... | 34,205 |
<p>Based on my research on convolution neural networks, every other layer in such a network has a subsampling operation, in which the resolution of the image is reduced so as to improve generalization of the network. So, a CNN could consist of an alternation of convolution and subsampling layers. However, when using ba... | 34,206 |
<p>I have two time series data sets which contain hourly-intervalled, monthly, and yearly household electricity consumption in kWh. One data set is produced by a simulation, the other gathered from the real-world. My aim is to validate the simulated output by using the data gathered from the real-world.</p>
<p>I want ... | 72,329 |
<p>I am having some problem in computing SVD and PCA in Matlab.
I do not know if I am doing theoretical mistakes or programming mistakes.</p>
<p>Starting with a data matrix $X$ PCA computes the eigenvalue $\lambda_i$ of the matrix $X^TX/(n-1)$.</p>
<p>On the other side for SVD $X=U\Sigma V^*$ and so $X^T X=V \Sigma^T... | 72,330 |
<p>There are two questions I feel puzzled in the recent period. </p>
<ol>
<li><p>Firstly, if given a set of sub-graphs, which are sampled from the underlying graph, how can I infer the underlying graph given the set of observed sub-graphs? If you can refer some good papers to me, I will appreciate it very much. This i... | 72,331 |
<p>I have several nonlinear curves of the transmission spectrum of a semiconductor. I got a fit to each of the curve. To get the chi squared for each my teacher gave me the formula $$\chi^2=\sum_{i=1}^{N}\frac{(T_{exp}-T_{fit})^2}{N\sigma^2_{exp}} $$ where $$\sigma_{exp}=\sum_{i=1}^{N}\frac{\sigma_{i}}{N}.$$ However, r... | 34,209 |
<p>My question is very simple: which learning resources (books, courses, online courses, and so on) about "large data analysis" would you suggest to a graduate with a strong background in Machine Learning and Computer Science?</p>
<p><strong>Edit:</strong> I am looking for something similar to section 17 of this very ... | 72,332 |
<p>What's a good measure of spread in a multidimensional space?</p>
<p>In a single dimension <em>variance</em> would be the measure I need, but in a multidimensional space I need more than just variances. Note that in a single dimension, I need something different than the <em>range</em> covered by the data points.</p... | 72,333 |
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