All Questions

8 views

Zero-intercept poisson regression model predicts better than a model with an intercept?

I have read some blogs/articles saying that intercept should not be suppressed. Recently, I used glmm.admb to model a ZIP (Zero-inflated Poisson) model which is giving better results without an ...
14 views

Regression without intercept [duplicate]

I saw that here explain how to get the formula for getting a regression without intercept but I already know it (for example in R you get it outomatic with ...
11 views

The econometrics of a Bayesian approach to event study methodology

Event studies are widespread in economics and finance to determine the effect of an event on a stock price, but they are almost always based on frequentist reasoning. An OLS regression -- over a ...
12 views

How to find rows of a given matrix that satisfy a certain property?

Suppose that I have a 90x4 matrix, say matrixgroup1, and some of rows are zero vectors. I want to find the rows that are not zero vectors. The code that I try was: ...
5 views

Is this problem convex ? (regularization term on xTw)

Suppose we want to solve the following: $$\min_{w} f(x^Tw, y) + \lambda g(x^Tw)$$ with $f$ a (logistic) loss and $g$ something like a variance. Is this a convex optimization problem ? What are ...
15 views

How to check that the selected features are not overfitting

I'm trying to select best features for sentiment classification for a set of reviews, and using penalized SVM and Logistic regression to perform such task. by basically iterating over different ...
33 views

Curious distribution

While checking my Android App Rating I saw this It's almost a quadratic progression! Is there any explanation for such a rating?
14 views

Is stratified meta-analysis more or less oblective than meta-regression?

Reviewer asked me why I use meta-regression as a way how to deal with heterogeneity among effect sizes instead of conducting stratified meta-analysis. I tied to google "stratified meta-analysis" and ...
8 views

Maximum Entropy classifier, high precision but low recall

I'm working on a sentiment analysis study of twitter data using the Maximum Entropy classifier. I've gathered dozens of thousands of tweets. To produce features, I used unigram, bigram and dictionary. ...
22 views

Hourly predictions using time series

I'd like to build a model based on time series. I have a dataset with records every 30 minutes for three months. What is the difference between modeling these data with the following kinds of ...
11 views

Finding maximum likelihood estimates of parameters of multiple normal populations

I've just started studying maximum likelihood and likelihood ratio tests. I've calculated the maximum likelihood of a normal population with unknown mean and variance. However, I've been given this ...
12 views

A reference for Pearson's chi-squared testing

I am wondering if there is a reference for the Pearson's chi-squared test suitable for technically-sophisticated audience that simply presents when the test (in its various forms) is appropriate and ...
7 views

Add data series to highlight cases on a box plot (Excel, SPSS or R)

first time user of this forum - guidance on how to provide enough information is very appreciated. I am trying to replicate the presentation of data used in the Medical education field. This will help ...
6 views

Application of Inclusion-Exclusion Principle for circular arrangements

N people are invited to a dinner party and they are sitting on a round table. Each person is sitting on a chair there are exactly N chairs. So each person has exactly two neighboring chairs, one on ...
26 views

What is maxout in neural network?

Anyone can explain what does maxout layer do in neural network? How to perform it? What does it different to normal activation function? I try to read the 2013 "Maxout Network" paper by Goodfellow et ...
11 views

Empirical confidence bands

Suppose I would like to evaluate how well, the following kernel density estimator $$\hat f (x) = \frac{1}{nh}\sum_{i=1}^nK\left(\frac{x-X_i}{h}\right)$$ works. I simulate data 1000 times and obtain ...
6 views

How to add a fixed variance structure do a GAM

I am using GAM to fit a smooth line to represent the recovery of timber stocks following forest harvest. The data is heterogenous and I do not want to transform it. I understand that a nice way to ...
10 views

Confidence interval of a function of Maximum Likelihood estimates

I have a probability density distribution for a variable $x$. This distribution is a function of another variable $Y$, that is $P(X=x \space |\space Y)$. I observe one $x$ value in nature (the ...
3 views

How would you get the standardized coefficients in errors-in-variables (EIV) regression?

I had some occasions to use the EIV regression in Stata, (and R, with the program built by Culpepper & Aguinis, 2011, "Using analysis of covariance (ANCOVA) with fallible covariates"), but I ...
14 views

Confusion about confusion matrix, or why 'power of test' + $\beta$ = 1?

Consider a confusion table summarizing the outcomes of $n$ tests of hypothesis $H_0$ for $n$ independent experiments: ...
50 views

Statistical significance of birth month of professional boxers

I looked at the birth dates of the top 100 ranked professional boxers of all time (67 of them to be exact). 40% of them were born during certain 3 month-long time periods. If birth date of boxers ...
28 views

What is the best visualization for Cramér's V?

When visualizing a linear correlation between two continuous variables, one uses a scatter plot, usually in combination with the Pearson product-moment correlation coefficient. When doing the same for ...
16 views

Best clustering algorithm for real state data

I want to cluster real state data to determine average price patterns in city and rural regions. My data set contains size, number of dorms, bathrooms and coordinates of the properties. Which would ...
13 views

Normality requirements across tests

I would like to understand the reason why normality is required in many tests. T-tests: I read that what needs to be normal is the sampling distribution rather than the sample distribution. But since ...
12 views

Combining multiple p-values

Is there any statistically relevant way to combine multiple p-values measuring different hypotheses but that are all trying to measure the same thing "in spirit"? Eg, if I wanted to measure some ...
7 views

How to analyse categories ranked 1 to 5 between two groups

I currently have 5 categories. I asked two groups to rank activities from 1 to 5: 1 is the most preferred activity and 5 the least preferred activity. How could I analyse this to see if there is a ...
12 views

cumulative uncertainty with time series predictive model

So I have a time-series with a set of variables a, b, c... and another measured variable y. What I do is using the initial state of a,b,c and y (at t0), I predict what y "should" be at the next time ...
109 views

Why Normalizing Factor is Required in Bayes Theorem?

Bayes theorem goes $$P(\textrm{model}|\textrm{data}) = \frac{P(\textrm{model}) \times P(\textrm{data}|\textrm{model})}{P(\textrm{data})}$$ This is all fine. But, I've read somewhere: ...
17 views

Two-proportion z test: is it best for my problem, and can I pool data from multiple “replicate” populations?

I am examining populations (cultures) of yeast cells and scoring them for a particular trait. The data is categorical; within a population, a yeast cell either has the trait or it does not. I wish ...
9 views

Combining different metrics to calculate composite score

Let's assume I have 3 metrics to evaluate a student. 1)Test Marks (0-50) 2)Weight of the student (KGs) 3)% Attendance (0%-100%) I want to calculate a total composite score which is a function of ...
4 views

fixed-effect nested factors in R with only SOME combinations present

I have a large data wth numerical response and two categorical factors: date and site. There are about 350 dates and 25 sites, but not all sites have observations on every single date (most have only ...
7 views

Confused about cross validation for model stacking

I'm reading section 8.8 of Elements of Statistical Learning, and though I keep reading the section on calculating the ensemble weights I'm missing something. It says that the stacking weights are ...
18 views

Model failed to converge

I'm doing a variable selection for the interaction gender:type2 now ...
23 views

What are parametric models? [duplicate]

The term Parametric Models does not sound unfamiliar to me, but I do not exactly know what they are. Can you please briefly explain what model is parametric and ...
10 views

Weibull Mixture question

Is it possible that a mixture of Weibull RVs is also Weibull distributed, and if yes, what are the necessary conditions?
34 views

Recommendation: Fast algorithm for logistic random effects?

What is the fastest algorithm for fitting a simple logistic 'random effects' type model, with only one level of categorical predictors? Another way of putting it might be a logistic regression with ...
26 views

Correcting data for mean but also variance

My data: I have data that range from 0 to 2 for numerous individuals. The scores are more or less normally distributed and vary continuously, but the scores are always between 0 at the minimum and 2 ...
15 views

Probability-generating function of two independent Poisson random variables [duplicate]

Let $X_1, X_2$ be two independent Poisson random variables with mean $\lambda_1, \lambda_2$, and $S_2 = a_1 X_1+a_2 X_2$, where the $a_1$ and $a_2$ are constants. Is it correct, that ...
13 views

Linear mixed models

I have some spatial measurement for two quantities, x and y. y is my dependent variable that I am looking to build a linear mixed effects model.Each point in space (lat,long) has one value of x, for ...
29 views

Classification Algorithms

Rather than due a google search and hope to find "the best" or an exhaustive list of classification algorithms I thought it might be easier to pose my questions here, and then get advice from you ...
6 views

R noobie here. I'm am trying to use a package that I download off of github using source_gist, but it appears that I need to re-download it every time I quit R ...
28 views

Curvilinear relationship with moderator

I am trying to moderate a curve and determine which equation I should follow. A simple curvilinear relationship has the following equation: (1) $Y = b_0 + b_1X + b_2X^2$ (i.e. a linear term and a ...
25 views

What to do after running an explorative factor analysis?

Say I asked 1000 people to evaluate 10 items about one product. The data looks like ID item1 item2 …item10 1 2 3….. After running an explorative factor ...
32 views

Determining probability mass function (PMF) using Bayesian approach

For instance, a person is trying to determine the light intensity (unit: Candela) from a source that he knows must be coming from one of the 3 mediums (A, B, and C). From his experience he have ...
17 views

Characterize this discrete distribution

Suppose we have $k$ buckets, with an infinite number of balls in each bucket. The balls within one bucket are indistinguishable, those between buckets are. We assign to bucket $i$ a probability $p_i$ ...
15 views

Multiple Regression - Converting Standardized Coefficients to Unstandardized

I recently performed a multiple linear regression using a standardized set of data, and I was wondering if it possible to convert the standardized coefficients from the regression into usable ...
21 views

Ordinal variable with 'don't know'

Can a variable that contains 'don't know' as a response be ordinal? For example, say the variable corresponds to responses to the question 'Do you agree with ...?' where the responses are: Agree ...
17 views

Paired T test vs 2 sample t test

I have been given data that includes 20 different households and what each household spends on grocery and restaurant. I need to run a t test and I'm not sure if I should use a paired t test or a 2 ...
What is the relationship between $p$ values and Type I errors
In hypothesis testing we set an accepted level of Type I error probability $\alpha$ and observe whether a sample statistic is equally likely or less likely to be observed if the null hypothesis was ...