All Questions

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Identifying multivariate outliers in a large sample with missing data, using SPSS

I'm a psychology PhD student doing analysis on a relatively large set of data, obtained via online surveys. The purpose of the study is largely to determine normative data for a population of adults, ...
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klaR package and the stepclass function

(R studio) Hi, I'm running LDA on a dataset with 250,000 observations, 2 classes and 30 variables. My goal is to create a classification model using the LDA function. After loading my variables I ...
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Is this a normal distribution?

Most of the data is on the line, I have transformed it using square root and log functions, however, it still seems to follow the line, but the extreme points deviate from the Q-Q plot normal line. 1. ...
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How to aggregate daily data, with a large amount of missing data?

I have a conceptual problem in a rather large study of the following design: technical details of a telephone connection are monitored daily, and at the end of the month a questionnaire is filled out ...
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Conjoint Analysis Problem: The File Does Not Exist

I want to ask, why every time I run Syntax data from SPSS, the output does not emerge as wanted? System warning says that my PLAN DATA does not exist, in fact I am very sure that the data does ...
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nls standard deviation calculation

I have fitted a non linear assymptotic equation to a set of data and my interest is in getting the standard deviations of the fitted parameters. Is this possible in nls?
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Building a predictive model, regression with a long right tail

I am trying to build a, regressive, predictive model for a target time-series that is heavily skewed. You could think of the target as being like earthquake magnitudes or heavy rainfall. Most of the ...
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Data analysis : replication, pseudoreplication and mixed models

I have several questions concerning analysis of data, especially when there are replications and/or pseudoreplications. First, I read an example in « pseudoreplication is a pseudoproblem » where we ...
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How to decide dynamic pricing for my items [on hold]

I have 10 items in my store and I am running 3 promotions. To maximize my sell and profit, I want to decide price for the items on daily or weekly basis. No of items=10 Promotions running-3 Other ...
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Unique matching for quantiles from one half of the density to a subset of the other half?

I am interested in finding the median absolute distance to quantiles. So, for $Q_\alpha$ the $0 \le \alpha \le 1$ quantile, I would like to find $Q_\gamma^*$ such that $Q_\gamma^*$ satisfies ...
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Statistical test: Does actual time series data deviate from forecast?

I have made a prediction of future sales based on an ARIMA model. The ARIMA model is based on past data, during which there has been no marketing activity. During the period predicted by ARIMA, I will ...
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correlation between 5 Likert scale and 7 Likert scale questions

I want to analyze the correlation between overall attitudes and purchase intention. Both are continuous variables. Overall attitude is measured using a 7 point Likert scale while purchase intention is ...
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Honglak Lee MNIST CDBN filter shapes?

This question is based on Honglak Lee's paper "Convolutional Deep Belief Networks for Scalable Unsupervised Learning of Hierarchical Representations". In chapter "4.3 Handwritten digit ...
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Hypothesis Testing with unidentified standard deviation [on hold]

A survey found that the average communication of male is 35 and the average communication of female is 65. The data obtained from 100 students from 2 samples and that the standard deviation were _ and ...
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Good way to categorize count data?

I want to use some count data to train a classifier. The count data range from 0 to 400 something. There are a bunch of smaller counts (0's and 1's). I wonder what would be a good way to categorize it ...
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Finding a percentile of joint, correlated distributions [on hold]

To give an economics example, lets say I have a distribution of House Price Indices (HPI) and Unemployment Rates - both non-normal and correlated to each other. I want to know how to calculate the ...
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When to use bootstapping in regression analyses?

When I run a regression analysis in SPSS, one of my predictor variables just fails to reach significance, p = .06. When I apply bootstrapping, the output tells me the predictor has a significant ...
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Example of two *correlated* normal variables whose sum is not normal

I am aware of some nice examples of pairs of correlated random variables which are marginally normal but not jointly normal. See this answer by Dilip Sarwate, and this one by Cardinal. I am also ...
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Finding the mode using grouping and analysis method [on hold]

class frequency 10-20 1 20-30 8 30-40 10 40-50 ...
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A/B testing zero inflated data

I am trying to conduct an A/B(/C) test to compare the performance of 3 different website pages but I'm facing issues regarding zero inflated data. I have data for each page regarding ...
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Is Wilcoxon test still valid if there is some shared information?

I have $N$ samples from a population, and to each sample I apply both method A and method B, recording the time each takes to run ($T_A$ and $T_B$, say) I then define a new pseudo-measurement for ...
38 views

How to best approach ANOVA with multiple response variables that might be correlated and Bonferroni Correction

I need some help verifying a simple analysis. I have completed a simple two factor experiment of more or less equal sample sizes. Let's assume for the case of this question that the sample sizes are ...
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Do I use ANOVA or MANOVA and why

I have a project for my thesis with both between groups subjects and within groups subjects. The independent variable is the program I am running and the dependent variable consists of 6 different ...
22 views

Requesting Advice on Coming up with my first ever research question [on hold]

I am new to this forum and apologize if this is posted in the wrong sub group. This past september I enrolled in advanced econometrics (a fourth year course at my college), and am now working on my ...
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Is calculating r2 appropriate for cox mixed effect models?

I'm looking at the effects of inbreeding on survival in a captive animal species. I'm trying to clearly distinguish the effects of inbreeding from other possible random genetic factors on survival. ...
9 views

Bayesian calculation of parameter multiplying normal

I am interested in a model like: $y_{i} = \sum_{k\in K}{\beta_{k} z_{k}}$, with $z_{k} \tilde{} N(\mu_{k}, \sigma_{k})$. where $\beta \equiv(\beta_{k})_{k\in K}$ is not known, but all else is. I ...
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Probability that the sample covariance matrix of a m.v. Gaussian exceeds a threshold

Let $\Sigma$ be a covariance matrix of $n$ data points in $\mathbb{R}^p$. So $\Sigma$ is $p\times p$. Suppose that the $n$ points are drawn from the distribution ...
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Pymc: Does this model call for Index, and if so, how would I use it?

I'm working on speeding up the mcmc for a hierarchical pymc model that is taking .2 seconds per iteration. It's the second model from this paper, modeling a soccer league using team-specific attack ...
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Does Deep network (e.g. # of hidden layer=2) always better than shallow network (i.e. # of hidden layer=1)?

I attempted to build a deep network (e.g. deep autoencoder) for some object classification, my result showed that the deep networks is worst than shallow network. However, from what I have read from ...
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Help in deriving unbiased estimator for a measure

There is a metric $H$ defined as = $\sum_{i=1}^{N} \min |u_i - u_j| * ..*|u_{i+d-1} - u_{j+d-1}|$ where $u$ is a multi dimensional vector of dimension $d$ and $u_i,u_j$ $\in \mathcal{R}^d$ are the ...
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AIS data modelling! [on hold]

I am interested in exhaust emission modelling with the use data received from vessels equipped with the Automatic Identification System (AIS). Are there any resources developed so far in relation to ...
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R: coherency matrix returned by spectrum is always 1

I am trying to understand what the coh value obtained from a call to spectrum means. I created a random 20x4 matrix and called spectrum on it. The ...
18 views

How to analyze relationship between data pairs

Please change the title if it's not accurate, I might be lacking terminology. I have two variables (x,y) which are directly correlated by pair. For example I have sampled 50 trees in my study area ...
10 views

Regression using a priori knowledge

I am sorry if the title (and probably the question) is not very clear but I have a regression problem which might be a bit over my head if I want to do it well. I am only interested in getting some ...
20 views

Do odds increase over time based on brute force?

Attempting to understanding a statistical concept which I'm positive is basic stats, but that I currently don't understand. Say that there's a one in ten million likelihood of an outcome happening ...
17 views

Reading in data set [on hold]

I am trying to read in this data set using R http://statweb.stanford.edu/~tibs/ElemStatLearn/datasets/nci.data I've tried several different things. Can anyone help me out?
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Independence of functions of Random variables [on hold]

I am working with two RV's X and Y X is distributed normally with mean=x and variance=x^2 Y is distributed uniform (0,1) I know this... ...
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Condition number of data matrix and stability of OLS estimates

I have a multivariate regression model $Y=X\beta ' + \epsilon$. The variables in the $X$ matrix have very different scales and hence the condition number of $X'X$ is huge (order of trillions). I ...
21 views

How to solve nonlinear optimization problem in R

Suppose I have a set of data and reason to believe the following relation holds y ~ a0 + a1*x1 + a2*x2 + a3*log(x3) How can I use R to solve for the coefficients {a0, ... a3}, supposing I want to ...
21 views

Pointwise probability limit

Suppose we have a joint distribution of a random sample $(y_n,x_n)\in R^2$: $$y_n = \beta_0 x_n + \epsilon_n$$ and the estimator  \hat \beta = argmin_\beta \frac{1}{N} \sum_{n=1}^N(y_n - \beta ...
11 views

Predictive analysis based on history

Let me first say that I am a CS person and my knowledge about statistics is quite basic. I am trying to see what predictive analysis to use for a problem I am trying to solve. I will try to make my ...
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Test(s) For Comparing qPCR results / ΔΔCт values

To be clear, I'm talking about real-time polmerase chain reaction (qPCR), not Principle Component Regression. Though from a company selling qPCR reagents, here is a good walk-through of the ...
12 views

Weights in Weighted Least Squares Regression

Let's suppose I have the following linear model: $R = \beta * X + \epsilon$ I have a cross-sectional time-series sample of $n$ stocks, at $T$ periods of time. Not all stocks necessarily have data ...
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Survey analysis: relationship between one discrete outcome variable and multiple categorical and ordered categorical variables

I have a data set that is the result of a survey. The survey asks the respondents to name 5 people in their community whom they turn to for advice. It then goes to these 5 people and asks the same. I ...
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Predict Seasonal Variations

I am developing an application related to pharmaceutical industry. Certain items are sold in significantly higher quantities during specific periods of the year. For example, here in my country, ...
16 views

Regarding Nested Anova in R

I would just like to double check if my approach to the following analysis was correct. Based on my design I have two treatments (A and B) with treatment A being comprised of 5 populations and B of 3 ...
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Unreliable and uncertainty of RF prediction results (multiple runs) for my data set

Currently, I meet such questions when building Random Forest model using my data set. My full data set: X_lab: 839 * 469 and y_lab: 839 * 1 which is for all labelled data and X_unl: 20346 * 469 which ...