# All Questions

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### Choosing samples of different sizes - considerations?

Let's say I have four populations with the sizes 2451, 2117, 7577, and 1545. For computational reasons I need to sample so that each sample has an N of maximum 1000. Assume that I have perfect control ...
9 views

### Improving a regression model based on diagnostics

I have two continuous predictors ($x_1, x_2$) in my data set and a continuous response variable $y$. The data set is by date for 6 quarters. Since I observed a clear pattern of surge during weekday ...
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### How do I interpret the p value returned in scipy's Mann Whitney U test?

I have a program in which I need to perform an action based on what results of a Mann Whitney U test are. I know the criteria that need to be met, but I would still like to understand what the results ...
7 views

### Salary Range Determination When Given Percentiles

Can one determine an accurate salary range (minimum, mid and maximum) if only provided the 25th, 50th and 75th percentiles?
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### Multiple, multiple regressions?

I have done a study on whether personality and demographics predict interaction on Facebook brand pages. I have used a Big five personality scale and the demographics include, sex, age, marital ...
4 views

### Baseline for Precision-Related Metrics

When working with ROC-AUC as a metric for binary classification, one often considers a value of 0.5 as a baseline from a random classifier (i.e. a data-blind classifier that randomly classifies test ...
7 views

### what is the best method of smoothing time series for product share data?

I am having a share data for products presribed over period of time.The share is calculated like for 3 products each one 1/3 share and like that,where products may vary and hence their share. What is ...
13 views

### Finding the range of parameters of a Probability Density Function

I have been given a probability distribution function as a homework. This function was taken from a book, as the lecturer claims. He says that the book gives it as a probability density function ...
27 views

### Why isn't Absolute Value used in Variance? [duplicate]

I'm a mathematics student self-studying statistics and I've run into a question. From what I can gather the variance of a population is found like so: $$\sigma^2 = \frac{\sum (X - \mu)^2}{N}$$ As ...
7 views

### Marginal Likelihoods for Bayes Factors with Multiple Discrete Hypothesis

If I have some data that I believe is Normally distributed and I just want to test the hypotheses that the mean is equal to 1 of 3 values, my understanding is that the Bayes Factor is the ratio of ...
17 views

### Is the mvrnorm function in Julia unstable?

I am trying to sample multivariate samples using mvrnorm in julia. Arguments are set as: mean5 = zeros(5) cov5 = the cor(z1, z2, z3, z4, z5), where z_i is calculated as x1,x2 ~Normal(0, 1) iiid ...
16 views

### Investigating interaction

Please I need to check for interaction before building an explanatory model (logistic regression). I have 16 interaction terms in total. Please how what is the best way to go about it. Will I need to ...
11 views

### Transform two correlated random variable to independent variables without knowing correlation

I am thinking about this interesting question which arises in the following realistic setting. For example, in one medical experiment one drug and one placebo are applied to two randomized groups of ...
12 views

### Comparison and testing multinomial coefficients

Straight to the problem I want to test the hypothesis that two coefficients of multinomial regression model are equal between them. For example, considering a model where Y is 3 level categorical ...
18 views

### Is there a way to evaluate observations of exponentially-distributed variables, where some of the observations are still “alive”?

I am looking at the tenure (i.e. elapsed time between hire date and termination date) of various employees in a system. I want to test the hypothesis that two groups of employees have the same tenure ...
12 views

### Aggregating forcast to higher spatial level

I am working on a project doing out of sample estimates of wheat yields at the village level in STATA. I am using a short panel 3 years and a sample of ~3000 villages. We are estimating a RE model and ...
18 views

### Forecasting a solar data using arima in R [on hold]

I have a solar data collected from a PV plant for the period 2009.the method for forecasting as suggested for me is to use a training set for instance from 01/01/2009 to 30/04/2009 and a test period ...
9 views

### Obtain the graph of the autocorrelation function in ARIMA models [migrated]

I am implementing an ARIMA model in Python for forecasting U.S. GDP. I am interested in obtaining the graph for the autocorrelation function. I obtained the values for ACF but I can not see the ...
10 views

### Finding genuine arrears and default arrears from rent payment patterns

I am currently working on some housing data - in particular analyzing the tenants' rent payment information and I am stuck on progressing with the following: I have to classify tenants based on their ...
17 views

### How to account for data taken at $t=0$ when using $\log(t)$ in the model? [duplicate]

I have a data set with four observations consisting of the variable $Y$ measured at time $t_0=0$ and at times $t_1, t_2$ and $t_3$. I would like to fit the following model: \log(y_j) = \alpha + ...
13 views

### Mean square error in log-linear model

Let's consider the following log-linear model: $log(Y_i) = \alpha + X_i\beta + \epsilon_i$ for i = 1, ..., N The fitted value is: $\widehat{log(Y)} = \hat{\alpha} + X\hat{\beta}$ Assuming ...
12 views

### Is there a way to add covariates to centile GAM curves in R?

Using the package "mgcv" I fitted a GAM to demonstrate head circumference changes over the lifetime for data stemming from two different countries; ...
10 views

### Reporting degrees of freedom for Welch t-test

The Welch t-test for unequal variances (also known as Welch–Satterthwaite or Welch-Aspin) generally has a non-integer degrees of freedom. How should these degrees of freedom be quoted when reporting ...
17 views

### How to verify that the ANN code is working properly?

First I'm not sure if this is the right place to post my question, but I saw some questions about ANN, and I assumed I can ask it here. I have implemented an ANN with back-propagation. I'm using it ...
8 views

### Should I use pearson correlation or MI test?

I'm relatively new to statistics hence my confusion. I am trying to measure the relationship between SMEs who do business in two markets and the level of tax compliance costs they face. The premise is ...
8 views

### I have set of data, I would like to understand the threshold for deciding good,average and poor [on hold]

I have a data of different visits of individual products to my website, I would like to segregate these based on a threshold. Currently there is a threshold set for good traffic, bad traffic and ...
86 views

### Is it unusual for MEAN to outperform ARIMA?

I'm relatively new to forecasting so I hope this isn't a ridiculous question. I recently applied a range of forecasting methods (MEAN, RWF, ETS, ARIMA and MLPs) and found that MEAN did surprisingly ...
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### Marginal effect calculation after logistic regression with panel dataset using R

I would like to perform a logit regression with a panel dataset, I know that the pglm package does the job, however, does anyone know if there is a standard package in R that allows me to calculate ...
14 views

### Post-hoc with Bonferroni a correction after ANOVA with repeated measure in SPSS

does somebody know where I can find the t value of post-hoc tests with Bonferroni correction when using SPSS.From what I get so far, I only see p values. Should I add a command in the script? Thank ...
11 views

### Testing and reporting interactions in multiple regression

I have a model with two between-participants predictors -- one continuous (a), and one categorical with two levels (b) -- and ...
21 views

### Range of Most Common Values

I have a few numbers such as: 24 65 62 63 39 52 88 21 65 65 62 75 Using Excel, I am looking to identify a range of numbers whose maximum and minimum are not more than 10% ...
11 views

### Should I standardize or rescale with polynomial regression as alternative to difference scores?

I am working with a model that uses polynomial regression combined with response surface modelling as an alternative to difference scores in regression: ...
10 views

### Number of instances in system vs. Number of instances left the system

This question is about these types of Poisson process: Poisson process (homogeneous) Non homogeneous Poisson process Compound Poisson process Let's assume that the 'serving time' is positive. ...
3 views

### making for making dataset for spam classifier

I'm trying to make a dataset for spam detection, what is the best automatic selection that I can use for picking up the word that should i count for my spam base ? Thank you
16 views

### nlme estimates near zero variance for the random effects

I am doing various analysis on a small sample. Basically, we have an experiment where 14 subjects (UID 1 ~ 14) used one of the 6 instruments (MID 1 ~ 6) on 3 occasions (Sequence 1 ~ 3). Each time an ...
84 views

### How to calculate $P (|X − Y | ≤ 1/6)$? [duplicate]

$f_{X,Y} \left( x, y \right) = 1\quad \text{for}\quad 0≤x≤1,\ 0≤y≤1$ and $0$ otherwise. How to calculate $P \left( |X − Y | ≤ 1/6 \right)$?
15 views

### How to plot model with forecasts in R? [migrated]

I recently upgraded R from 2.x to 3.1 and I feel like there were some changes that I am not aware of with regards to plotting models. ...
5 views

### Why does aov consider a 3x3 factorial design unbalanced?

I have a two factor, bot at 3 levels with all factor levels, and with 5 replicates for each. This is a standard 3^2 factorial design, and yet aov gives the message "Estimated effects may be ...
15 views

### Making a neural network model more sensitive to one of its several inputs

I am currently using neural network methods in R to model energy consumption (response) based on temperatures, previous consumption values and weekend dummy variables (inputs). Unfortunately, the ...
16 views

### Sampling according to a difference of two normal distributions

Assuming that I have two normal distributions $p_1(x)$ and $p_2(x)$ and I can draw samples efficiently from them. Now, I can easily draw samples from $p(x) = 0.5 p_1(x) + 0.5 p_2(x)$ by with 50% ...
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### Vowpal wabbit and SGD divergence

I have the following vowpal wabbit log. To me it looks quite counter-intuitive: the objective function (l1-regularized hinge loss) seems to go down then suddenly spiking up. I am aware that gradient ...
8 views

### Coarse-resolution subsampling of time-series data

Suppose I have time series data with a very fine resolution, e.g. 100 datapoints per second. I want to report this data to some service that can only take data at 1 point per second. I need to do ...
6 views

### Linear time series model and z transform

I am few questions from the following papers: ...
21 views

### SVM Dual Formulation :: KKT Constraint

In Andew Ng's SVM course notes, the final hard margin optimization problem is given as the following: I am unclear how to see from this where the 5th constraint is satisfied. The definition of ...
7 views

### Support vector regression in weka

I am using SVR for statistical down-scaling of precipitation. I have taken the first 3 factor scores in principal component analysis of variables as predictors and precipitation as predictand. As ...
38 views

### How should I model interactions between explanatory variables when one of them may have quadratic and cubic terms?

I'm sincerely hoping that I have phrased this question in such a way that it can be definitively answered--if not, please let me know and I will try again! I should also I guess note that I will be ...
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### Spambase Naive Bayes

i'm wondering about spambase which was created by Mark Hopkins, Erik Reeber, GeorgeForman, et all. how is the method for pick each word for attribute comment. Can somebody tell me the journal because ...