question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>If I have the below functional form for an OLS regression, how do I interpret the $x$ and $x^2$? I cannot interpret them separately, correct? Do I interpret them as a summation of the two coefficients, so the effect of a one unit change of $x$ on $y$ is $0.5 + 0.3 = 0.8$?</p>
<p>$$
y = a + 0.5x + 0.3x^2 + e
$$</p>... | 69,213 |
<p>I would like to know how do we analyze or regard the Neutral response (such as Don't Know) in a questionnaire using the following Likert Scale:</p>
<p>1:Strongly Disagree 2:Disagree 3:Don't Know 4:Agree 5: Strongly Agreee</p> | 69,214 |
<p>I am using
spec.pgram(tsobj,spans=6, plot=TRUE)
to obtain a periodogram for my univariate time series of monthly observations which were sampled over 86 years (so I have 1032 observations in total). It's defined as an object of class "ts" with frequency=12. The periodogram nicely depicts the seasonality for 1 y... | 30,084 |
<p>My research involved a questionnaire with open-ended questions, multi-answer multiple choice (select all that apply; entered as "1" for circled answers, "0" for non-circled), and likert scale questions. I want to examine whether there are differences in responses to the survey (especially the likert questions) based... | 69,215 |
<p>I would like to run a stationarity assessment test on a 2D signal. Is there a suitable test, e.g. a 2D DF or ADF, etc?</p>
<p>Thanks.</p>
<p>Edit:
A 2D signal is a signal defined on a lattice, i.e. instead of a time-series, <code>x[n]</code>, we have <code>x[m,n]</code>, where <code>m,n \in {0,1,...,N}</code>.</p... | 69,216 |
<p>I've got two sets of data from some fluorescent cells.</p>
<p>The first set is when the cells don't have their fluorescence switched on, but they are still faintly glowing.</p>
<p>The second set is when they do have their fluorescence switched on.</p>
<p>I ran each of the two experiments three times, so n=3, and ... | 69,217 |
<p>I have one qualitative factor (Treatments) and two uncontrollable factors, temperature and moisture, with one response variable. I'm confused whether I should use ANCOVA with temperature and moisture as covariates or Taguchi methods can be used for this problem. Any advise and point to reference will be highly appr... | 69,218 |
<p>I have the sample size, mean and standard deviation for the number of births per year for my county, but I'd like to transfer that information to a smaller population within the county (ie. a school within the county).</p>
<p>So in this situation, in the age group I'm concerned with, the population of women in the ... | 29,576 |
<p>$\sigma c=\sqrt{\overline{R}(\sigma S)^{2}+\overline{S^{2}}(\sigma R^{2})}$
where,</p>
<p>$\sigma c$ --- the buffer stock --- needed for maintaining the risk
of stockouts, is used by logistitians</p>
<p>$\overline{R}$ --- the mean of the reserves</p>
<p>$\overline{S^{2}}$ --- the mean of the production</p>
<p>$(... | 69,219 |
<p><strong>The situation:</strong></p>
<p>I have a logistic model that should predict a defect (<code>1=defect, 0=no defect</code>). My model uses 4 out of 14 parameters, which are significant for my dependent variable (tested through <code>summary()</code> and the <code>anova()</code> chi-squared test). Furthermore, ... | 29,577 |
<p>Let $ Y_1 < Y_2 <\ldots <Y_{10}$ be the order statistics of a random sample from a continuous type distribution with cdf $F(x)$. How would I begin to show that the joint distribution of $V_1=F(Y_4)-F(Y_2)$ and $V_2=F(Y_{10})-F(Y_6)$ is given by:</p>
<p>$$h(v_1,v_2)= \frac{10!}{1!3!4!} v_1 v_2^3 (1-v_1-v_2)... | 69,220 |
<p>I need some help on this analysis.</p>
<p>I have 3 groups of individuals, different the level and kind of physical activity.</p>
<p>For each individual I have the heart rate, taken every minute for ~24h. (each person has a <strong>slightly different number of measurement</strong> due to differences in observation ... | 69,221 |
<p>I am wondering if anyone has suggestions on which statistical test would be appropriate to compare demographic data obtained from 1900 Census schedule sheets? I have a database of boarding school student information (age, gender, race, birthplace,...) for 25 different boarding schools across the country. I want to c... | 69,222 |
<p>Is there a statistical procedure that can measure the concordance between two sets of data that have, say, a sinusoidal tendency?</p> | 29,581 |
<p>Does Lin's <a href="http://en.wikipedia.org/wiki/Concordance_correlation_coefficient" rel="nofollow">concordance correlation coefficient</a> assume that the 2 data sets have linear or monotonic tendencies? Or, can I measure the concordance between 2 data sets that have a sinusoidal tendency?
Thanks
NG</p> | 29,582 |
<p>I have the test results of a blood test administered to 2500 people four times at six-month intervals. The results primarily consist of two measures of immune response - one in the presence of certain tuberculosis antigens, one in the absence. Currently, each test evaluates to either positive or negative based on ... | 69,223 |
<p>I have been using Matlab for my work, but I have started learning Python lately. I employ statistical analysis, more precisely geo-statistics, in my work. I was wanting to ask, from your perspectives, which one among the two languages is good for general statistical/data analysis? What are the pros and cons, other t... | 37,482 |
<p>Consider this example:</p>
<pre><code>team <- rep(c("A","B","C"), times=c(7,4,10))
trip <- rep(NA,length(team))
for(i in 1:length(unique(team))){
trip[which(team==unique(team)[i])] <- 1:days[i]
}
obs < -c(rnorm(days[1],100,30), rnorm(days[1],100,5), rnorm(days[1],100,15))
data <- data.frame(team, ... | 69,224 |
<p>Suppose I want to measure similarity between users. If two users match on an item that is very improbable, I want to give greater weight to that.</p> | 69,225 |
<p>I'm working on a "player phylogeny" to help make comparisons between potential NBA draft picks and current players. An example is shown below:</p>
<p><img src="http://i.stack.imgur.com/giv5V.png" alt="enter image description here"></p>
<p>I'm using the dist() function in R, and am assuming that all factors are equ... | 37,466 |
<p>I'm looking for help in determining how to equate the following:</p>
<ol>
<li>We have a surface of 13 cm X 10 cm. </li>
<li>We have a 95% probability of hit
on a 16 cm diameter surface.</li>
</ol>
<p>I would like to equate $B$, probability of hit to the 13cm X 10 cm surface. 95% probability of hit on a circle of 1... | 69,226 |
<p>I recently studied two asymmetric <em>t</em> distribution both with a name of <em>skewed-$t$</em>. I am confused with their differences or are they actually the same?</p>
<p>The first one is introduced by Hansen (1994) with pdf:</p>
<p>$f(x;\nu,\zeta)=\begin{cases}
\begin{array}{cc}
bc\left(1+\frac{1}{\nu-2}\lef... | 69,227 |
<p>I have birds translocated from site A (original, capture site) to site B (new, release site) and I want to analyse homing behaviour. Translocation of individuals was performed continuously (several weeks), thus a <strong>bird released at the beginning of the experiment had theoretically highest chance to be recaptur... | 29,588 |
<p>I have a question (simpler than my previous post today I hope!), which is probably very stupid as nobody has never asked it before. </p>
<p>Lets say I am trying to explain the effect of 3 variables (A, B and C) on a dependent one (Y). Biologically speaking, A and B should really have an effect on Y. So I am testing... | 29,590 |
<p>I am in charge of quality control of n = 400 reports. Most of the quality checks are automated, but some have to be manual. I need to figure out how many reports my team needs to check manually in order to be fairly confident that all of the reports are error free in the areas which require manual checks. How can... | 42,225 |
<p>After reading some material, I found few options for defining train and test sets:</p>
<ol>
<li>Just splitting with no change.</li>
<li>Accumulating/moving window of train set.</li>
<li>Leave a relatively small (warming) period between test and train sets, and then use window again (including the warming period).</... | 3,981 |
<p>I am quite new with R and while i am able to perform the basics i am not yet able to understand the output results. For example:</p>
<p><code>summary(lmodel)</code> generates the following:</p>
<pre><code>Call:
lm(formula = temperature ~ altitude + sea.distance, data = meteodata)
Residuals:
Min 1Q Me... | 49,310 |
<p>I am fairly sure that I understand the how Monte Carlo integration works but I am not understanding the formulation of how it is used to estimate Pi. I am going by the procedure outlined in the 5th slide of this presentation <a href="http://homepages.inf.ed.ac.uk/imurray2/teaching/09mlss/slides.pdf" rel="nofollow">... | 69,228 |
<p>I'm trying to estimate the state of a Gaussian random walk with central tendency based on time series measurements with varying uncertainties. My random variable has the following form:</p>
<p>$ \frac{d x}{d t} \equiv F(t) - \alpha x $</p>
<p>Where F is a Gaussian random variable. I've noticed that this problem ... | 29,594 |
<p>Poisson derived incidence rates can be fairly nice in medical research.</p>
<p>I noted this beautiful comparison in The Lancet:</p>
<p><img src="http://i.stack.imgur.com/VrmQe.png" alt="enter image description here"></p>
<p>I believe that kind of calculation, when accompanied by a Cox regression is quiet informat... | 69,229 |
<p>I have an iterative document classification task, corpus size = 300,000 documents. The labels are binary valued (yes/no). I wanted to know whether the following methodology is valid. The assumption is that there is an oracle to label the documents.</p>
<p>Randomly select 500 documents and label them using an oracle... | 29,596 |
<p>Is summation of logarithm of a random variable equal to the logarithm of the sum of the random variable. </p> | 69,230 |
<p>Suppose I have two discrete random variables, $P$ and $Q$, with probability mass functions given by $p(x)$ and $q(x)$. I know that these random variables are multinomials, generated by choosing $K = 5$ English words each. Therefore, a sample of $P$ looks like a very long vector, in which the $i$th entry is the num... | 29,605 |
<p>Let $Z=(Y, X)$ be an observation from a distribution $P$ where $Y$ is a response variable and $X$ is a vector of regressors. Assuming the following model:
$Y = F(X'\beta, u)$ where $X'\beta$ is a linear index, $u$ is a random disturbance ($u \perp X$) and $F$ is a strictly increasing function in each of its argument... | 29,607 |
<p>If I have several hundred coefficients generated by running multiple variable regression model (keeping it as broad as possible by not specifying the nature of the predictors and outcome variable), it would appear to me that I have two options for assessing the significance of any one result.</p>
<ol>
<li><p>Identi... | 69,231 |
<p>For example, if I was to plot a trendline in Excel I can choose to include its formula on the chart, it will display something like <code>myY = 0.5 + 0.5 * myX</code>. </p>
<p>R has quite advanced functionality for creating sophisticated mathematical expressions, so I assume this is fairly straightforward to do. ... | 26,846 |
<p>In the first step of modeling a regression equation I came up with the following model:</p>
<p>$T_c = 26.73 + 0.042{\rm Sc} + 0.247{\rm Lc} - 14.709{\rm Lf} + 1.41{\rm Lu} - 0.214{\rm Fc} + 0.041{\rm Ad} - 64.308{\rm Sr} - 20.341{\rm Rc}$</p>
<p>Analyzing the residuals it is obviously noticed it does not follow a ... | 29,608 |
<p>I am required to show that the following accept/reject algoritmh produces observations from a beta distribution with parameters $\alpha$ and $\beta$.</p>
<hr>
<ol>
<li>Generate $U_1$ and $U_2$ iid uniform(0,1) random variables. Set $V_1=U^{1/{\alpha}}$ and $V_2=U_2 ^{1/{\beta}}$</li>
<li>Set $W=V_1+V_2$. If $W\leq... | 29,609 |
<p>I have two time series which are sampled at the exact same times. I would like to calculate a confidence interval either for the ratio between the two or the difference between the two. The values tend to be somewhat similar, but both have a large amount of what looks like random noise superimposed on them (much l... | 26,868 |
<p><strong>Short question:</strong>
I am looking for books that deal with correlated data in a systematic and theoretical way. </p>
<hr>
<p><strong>Long version:</strong></p>
<p>Right now I am developing approximation algorithms for time series data (more concrete I want to approximate a function $f:[a,b]\rightarro... | 69,232 |
<p>Let $0< \delta<\frac{1}{2}$. Why do we have for $X_{1},X_{2}$ iid:</p>
<p>\begin{equation}
\{X_{1}+X_{2}>x\}\subset\{X_{1}>(1-\delta)x\}\cup\{X_{2}>(1-\delta)x\}\cup\{X_{1}> \delta x,\ X_{2}>\delta x\}?
\end{equation}</p> | 69,233 |
<p>I would like to test for a correlation that is zero or negative using the following hypothesis test:<br>
$H_0: p>0$ (Null hypothesis: the correlation is positive)<br>
$H_A: p\le0$ (Alternative hypothesis: the correlation is zero or negative)</p>
<p>Since this is different from the usual correlation statistical h... | 69,234 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/2717/clustering-with-a-distance-matrix">Clustering with a distance matrix</a> </p>
</blockquote>
<p>I have a set of data which I wish to cluster.</p>
<p>I have computed a distance measure between each pai... | 49,683 |
<p>I'm trying to design a statistics package in .NET, and I'd like to apply object-oriented design principles to some of the data structures that I'm developing.</p>
<p>As I look through sample data sets for simple classifiers, even though there exist other types of attributes (ordinal being the only other one I've se... | 69,235 |
<p>I have a task that is specific to inventory management that is currently driving me crazy. To summarize the problem: We regularly must monitor inventory settings to ensure that they represent true demand, to ensure that we are not overstocking nor understocking. The standard procedure is to schedule reviews, where h... | 39,787 |
<p><strong>Is drawing a scatter plot, with fitted regression lines for subgroups, the way to graph a possible interaction in SPSS?</strong></p>
<p>I may be missing something but I could not find a specific way to do it. I have only just migrated to SPSS from Excel!</p>
<p>My IV and DV are interval scale measures and ... | 69,236 |
<p>Let $\{W_t,t \geq 0\}$ be a standard Brownian motion under $\mathbb P$. Let $T_a$ be the hitting time of level $a$, that is:
$$T_a= \text{inf}\{t \geq 0:W_t=a\}.$$
From a proposition, we know that
$$\mathbb E[\exp(-\theta T_a)] = \exp(-a \sqrt{2\theta}).$$</p>
<p>How do we make use of the above preposition to calc... | 69,237 |
<p>Is a normalized version of an exponential family distribution still an exponential family distribution? Here "normalized" means making its mean zero and variance one.</p>
<p>According to the following definition of an exponential family distribution from <a href="http://en.wikipedia.org/wiki/Exponential_family" rel... | 69,238 |
<p>I am having some doubts on whether I should use binary or multinomial logit.
I am modelling product choice. The dependent variable is the choice of either shampoo or toothpaste. Although my dependent variable has two outcomes, I am wondering whether it is appropriate to use multinomial logit instead of binary. </p>
... | 29,619 |
<p>I have a number of animal observations, and want to deduce the number of territories (i.e. the number of individual animals) from this.</p>
<p>More formally, the problem can be stated as follows: Each observation is a triple consisting of two coordinates and a date. Observations on the same date are assumed to be d... | 29,623 |
<p>I have an experiment with two treatments (3 & 4 factors each) and 4 true replicates on 48 plots. Those experimental plots recruited various quantities of 25 different species so the dataset has 1200 data points. </p>
<p>My question is this: if I run a GLM ANOVA on the two expt tmts and their interaction, but n... | 69,239 |
<p>I have a data-set of genetic variants which I'm trying to use as predictors for a simple phenotype, and for starters I use a binary logistic regression in SPSS. I have around 900 individuals, and for each individual around 50 variations and a phenotype.</p>
<p>However, I get an unreasonably high amount of removed v... | 39,791 |
<p>I'm running the Boruta algorithm with a $179\times 36$ predictor matrix and a numerical response. Most of the variables have a score going to <code>-Inf</code>. Should I conclude there are not important or there's a problem ?</p>
<pre><code>bor <- Boruta(X,y)
> dim(X)
[1] 179 36
> bor$ImpHistory[,1]
[1]... | 29,626 |
<p>I have a set of experiments that I'd like to run some significance tests over. It looks like:</p>
<pre><code>Word Feature Model Test Score Correct Total
allow.v woc hac zellig 0.382353 26 68
allow.v woc hac bellig 1.000000 0 0
allow.v woc kmeans zellig 0.382353 26 68
allow.v woc kmeans bellig 1.000000 0 0
run.v wo... | 69,240 |
<p>Sometimes, I just want to do a copy & paste from the output window in SAS. I can highlight text with a mouse-drag, but only SOMETIMES does that get copied to the clipboard. It doesn't matter if I use "CTRL-C" or right click -> copy, or edit -> copy</p>
<p>Any other SAS users experience this, and do you know a w... | 39,793 |
<p>I've heard that when many regression model specifications (say, in OLS) are considered as possibilities for a dataset, this causes multiple comparison problems and the p-values and confidence intervals are no longer reliable. One extreme example of this is stepwise regression.</p>
<p>When can I use the data itself ... | 69,241 |
<p>I am using both R and SAS for the time series modeling. There is an option in SAS that I could not find so far in any packages developed in R for the time series modeling such as TSA or forecast package, at least to the best of my knowledge! To explain more, if we use the windowing environment in SAS to fit an ARIMA... | 29,630 |
<p>I have two scales measuring the same construct, and I would like to know which scale is distributed more closely to a normal distribution. There are various possibilities for comparing a distribution with a normal distribution (e.g., kolmogorov-smirnov test, etc.), but is there any possibility to compare the devianc... | 69,242 |
<p>I have a database with many thousands of entries of box scores. Each box score has a player name, date played, points scored, minutes played, and some other stats like rebounds, assists, etc. I want to use this information to find out how the frequency of points per game varies by each half a point difference. I'... | 69,243 |
<p>What are the <strong>variable/feature selection that you prefer</strong> for binary classification when there are many more variables/feature than observations in the learning set? The aim here is to discuss what is the feature selection procedure that reduces the best the classification error. </p>
<p>We can <str... | 49,653 |
<p>I am trying to model data on the number of online sales are made within a fixed sale period of 3 days. Data are generated only when the sale is made. I think for this kind of data I will be using a type of time series model for count data with inflated zero samples. But this dataset adds one more layer of complexity... | 39,798 |
<p>I am proposing to try and find a trend in some very noisy long term data. The data is basically weekly measurements of something which moved about 5mm over a period of about 8 months. The data is to 1mm accuracey and is very noisy regularly changing +/-1 or 2mm in a week. We only have the data to the nearest mm. </p... | 69,244 |
<p>I am in the process of performing ordinal regression on a large data set that measures different types of variables (nominal, ordinal, continuous). My outcome variable is ordinal, hence the ordinal regression. My question is; can I include nominal data (e.g. a binary coded variable representing a 'yes/no' response) ... | 47,553 |
<p>Let's say I got a Gaussian Process model $M$ based on some training data. Now I get a stream of sample data of a certain batch size coming in.</p>
<p>The GP does not model a time series, but it's trying to regress the value at certain locations $x$, that will be visited mutliple times.</p>
<p>I know that at some p... | 47,555 |
<p>I don't feel very comfortable with stats (still using simple programmes like SPSS rather than R!), and have a question about which is the best test to use with the following design: </p>
<p>I have performed an experiment with n = 4 per group (three groups: drug A+ drug B treated, drug A+ vehicle treated, vehicle on... | 69,245 |
<p>When running a logit/probit model for particular sets of outcomes on a set of participants (whether they did a certain behavior at least two times), how can one best control for differences when the individual observations began? In particular, one person may have started to participate 3 years ago, whereas another ... | 69,246 |
<p>For each function (f or g) I have some sampled X data (of about 1000 dimensions) and the associated (noisy) y value. From these two data sets I would like to estimate f-g, whose magnitude I expect to be small relative to f and g. The X data for both datasets are drawn from the same distribution. I have tried estim... | 69,247 |
<p>I have already posted this question in the quant section, maybe the statistics community is more familiar with the topic:</p>
<p>I am thinking about the time-scaling of <strong>Cornish-Fisher VaR</strong> (see e.g.page 130 <a href="http://cran.r-project.org/web/packages/PerformanceAnalytics/PerformanceAnalytics.pd... | 39,804 |
<p>I have microfossil data from across the Cretaceous-Tertiary boundary, 20 species (=variables) and 27 samples (=observations). I have run a PCA with varimax rotation on these data using the rgr package. I now want to determine the significance of the PC loadings using bootstrap BCa confidence intervals from package b... | 69,248 |
<p>I am a beginner and in the process of understanding PCA.
I came across the following question</p>
<blockquote>
<p>Suppose we have a data set where each data point represents a single student's scores on a math test, a physics test, a reading comprehension test, and a vocabulary test. </p>
<p>We find the fi... | 69,249 |
<p>I would like to predict using a linear model in R. The model that I have is of the form <code>lm(y~ lag(x))</code>. It seems like I should be able to predict using the predict function, but this does not look ahead into the future. </p>
<p>Here is the lag function that I have been using from within R. </p>
<pr... | 29,641 |
<p>So I've been dealing with a problem concerning the change in market share. I have the total volume generated (dollars for instance) and number of transactions that those volumes are generated from. As in below:</p>
<pre><code> Total Volume Volume of X Share of X(vol) N_Total N_X Share of X(in N)
P... | 69,250 |
<p>I have used a psychometric survey of 10 items which measure risk perception.
I have taken the mean scores of these 10 items from a sample of 355 respondents who rated six hazards via the 10 Psychometric questions. I have performed a multiple regression where my criterion variable is a weighted composite scale from ... | 69,251 |
<p>I want to do a survey about the quality of a slot game. At the end of a game session (when player cashes out), there will be a question on screen:</p>
<p>"Please rate the game on a scale of 1 to 5"</p>
<p>Player can touch to rate. I can foresee 2 bias sources:</p>
<ol>
<li>Whether player won or lost</li>
<li>Whet... | 870 |
<p>If I have a random variable $V$ that is normally distributed with some $\mu$ and $\sigma$, then what is the expected value of $1/V$? I tried doing by delta method, and I get expected value $1/\mu$, but I also read that this is not the correct result.</p>
<p>To clarify:</p>
<p>My random variable $V$ is a variable t... | 29,646 |
<p>Sometimes in pattern recognition say Character recognition, Hamming distance is used although there are other distance measures. But if the pattern is represented in (1,0,-1) then Hamming distance is easier (Reference : Effect of Hamming distance of patterns on storage capacity of Hopfield Network). In my applicatio... | 29,647 |
<p>I have difficulties with <em>Likelihoods</em>. I do understand Bayes' Theorem</p>
<p>$$p(A|B, \mathcal{H}) = \frac{p(B|A, \mathcal{H}) p(A|\mathcal{H})}{p(B|\mathcal{H})}$$</p>
<p>which can be directly deduced from applying $p(A,B) = p(B) \cdot p(A|B) = p (A) p(B|A) = p(B,A)$. Thus in my interpretation, the $p(\cd... | 69,252 |
<p>I am analyzing a set of clinical data where I try to predict an outcome by using certain covariates. I have already done univariate analysis and now am progressing to binary logistic regression, incorporating the covariates that have a p < 0.1 in univariate tests to the model.
In doing binary logisitic regression... | 69,253 |
<p>How can I generate two correlated ARMA(1,1) data series where</p>
<p>$d_{1,t}=\mu+\phi_{1}d_{1,(t-1)}-\theta_1(e_1(t-1)+e_1(t))$</p>
<p>$d_{2,t}=\mu+\phi_{2}d_{2,(t-1)}-\theta_2(e_2(t-1)+e_2(t))$</p>
<p>and $\rho_{12}$ is desired correlation between $e_1$ and $e_2$?</p> | 69,254 |
<p>Does it make sense to use the differences in p value to show a tendency or the 'importance' of the effect of a treatment. for example, I have treated a contaminated soil and I test the treatments against one control. I can see the high molecular weight contaminants are more affected by the treatment and that the <st... | 69,255 |
<p>I have 4 IVs in my model that directly effect the DV.
The <a href="https://docs.google.com/document/pub?id=1_4sDxvwFLY0-SBvW8llkURv23My89Vc06ZNbepCcHAw" rel="nofollow">results</a> of the correlation & regression analyses showed that:</p>
<p><strong>IV1&DV:</strong> </p>
<p>Pearson Correlation Coefficient: ... | 29,650 |
<p>Okay this is my problem: </p>
<ul>
<li>I have 12 participants.</li>
<li>Each participant spent 3 nights in my lab doing a reaction time task at four timepoints during the night(12, 1, 2 and 3 oclock), with one week between each of those nights.</li>
<li>Each night, each participants was exposed to one of three expe... | 37,558 |
<p>So I've been asked today in class why you divide the sum of square error with $(n-1)$ instead of with $n$, when calculating the sd.</p>
<p>I said I am not going to answer it in class (since I didn't wanna go into unbiased estimators), but later I wondered - <strong>is there</strong> an intuitive explanation for thi... | 49,397 |
<p>Most standard distributions in R have a family of commands - pdf/pmf, cdf/cmf, quantile, random deviates (for example- dnorm, pnorm, qnorm, rnorm).</p>
<p>I know it's easy enough to make use of some standard commands to reproduce these functions for the discrete uniform distributions, but is there already a preferr... | 49,383 |
<p>I am using the <code>grm</code> function in the <code>ltm</code> package in R. There is no function to check the goodness of fit of the output. How can I check if the graded response model is a good fit to the data?</p> | 29,653 |
<p>Say I run a Monte Carlo simulation to generate a regression model of a simulation space. All variable parameters in the original sample have been selected at random from a uniform distribution.</p>
<p>Is it then possible to resample from this sample while constraining one or more of the variables to a new distribut... | 69,256 |
<p>If my dependent variable is a technique scored as 1 for correct step and zero for incorrect can I use Friedmans test to compare technique scores at 3 time points?</p> | 37,559 |
<p>I designed a simple survey about cancer knowledge among adults. There will be two groups: Those that have first-hand experience with cancer (you or someone in your immediate family with cancer) and those without (negative on the above). There are seven questions related to cancer knowledge, each with one right an... | 69,257 |
<p>I have a set of data that has $n$ samples described by $m$ variables. I do a PCA to reduce it to just 2 dimensions so I can make a nice 2D plot of the data. I understand that the $x,y$ coordinates (i.e., the PCA scores) for the plot are calculated by basically summing the products of the original data (after centeri... | 69,258 |
<p>Currently, I am doing a clustering analysis for two sets of data. One smaller dataset (about 100 data) got ground truth labels, and one larger dataset (about 2000 data) has no ground truth labels.</p>
<p>For the smaller dataset, obviously, I can obtain quantitative results like accuracy, sensitivity and specificity... | 69,259 |
<p>I have performed an experiment to test the cellular sensitivity to a certain DNA damage agent. We have found 270 genes that were specifically sensitive to the drug and the total number of genes analyzed was 3668. 38 out of the 270 sensitive genes are classified as "DNA repair genes". If the number of "DNA repair gen... | 69,260 |
<p>Please pardon me if this question is not clear. I am not sure if I am using the right terminologies.</p>
<p>I have conducted an experiment in different environments multiple times. So my data looks something like this:</p>
<pre><code>Environment1 1.2 2.1 1.1 1.5 1.6
Environment2 4.2 2.6 3.5 2.5 2.9
Envir... | 69,261 |
<p>I would like to do a one-sided Fisher´s exact test for an analysis. I have not any statistic software to obtain the pvalues (no SAS, no SPSS). The 2x2 tables are of this type:</p>
<p>Do you know any online statistical software to calculate the pvalues? I have tried with some of them but the results indicate pvalue&... | 69,262 |
<p>I have a problem where the crucial variable is the integral of the squared PDF of a random variable, i.e.</p>
<p>$\int f(x)^2dx$</p>
<p>How should I interpret this property of a distribution? If $f(x)$ is gaussian, then this is inversely proportional to the variance, $\sigma^2$, but I don't think this is generall... | 49,825 |
<p>I need any solved example/data set which explain how to apply Bayes Theorem for continuous value attributes. I read the book (Machine Learning by Tom Mitchell) and found this equation. But I need some data to verify that I've understood this concept.</p>
<p><img src="http://i.stack.imgur.com/pmjKA.png" alt="Equatio... | 69,263 |
<p>I am having some issues understanding how unsupervised Random Forest works according to <a href="http://www.stat.berkeley.edu/~breiman/RandomForests/cc_home.htm#unsup" rel="nofollow">Breiman</a>. I only have unlabeled data, so the thought arose to use unsupervised Random Forest and use the resulting dissimilarity ma... | 29,659 |
<p>How do I calculate the correlation using ordinal data based on a 5-point Likert scale associating perioperative education to patient satisfaction scores? A numerical value (<code>1</code>: strongly agree – <code>5</code>: strongly disagree) will represent the participant's perception of satisfaction as a patient ... | 49,730 |
<p>In many cities, neighborhood Crime Watch groups are formed in an attempt to reduce the amount of criminal activity. Suppose one neighborhood that has experienced an average of 10 crimes per year organizes a Crime Watch group. During the first year following the creation of the group, 3 crimes are committed in the ne... | 69,264 |
<p>I want to construct a $3^{5-2}$ design with $I=ABC$ and $I=CDE$ as generators. The complete defining relation for this design is: $I=ABC=CDE=ABC^{2}DE=ABD^{2}E^{2}$. This is a resolution III design with $x_4=2x_1+2x_2+x_3$ and $x_5=x_1+x_2+2x_4\:({\rm mod}\:3)$.</p>
<p><strong>Question</strong>
I wonder how to get ... | 69,265 |
<p>This is the question I am trying to answer : I’m working on a thesis project and have a variable that is normally distributed and related to happiness. I am considering to split my sample into depressed and non-depressed and run the correlation and the rest of the analyses that way. I think it will help clarify the ... | 29,664 |
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