All Questions

0
votes
2answers
7 views

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 ...
0
votes
0answers
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 ...
0
votes
0answers
8 views

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 ...
0
votes
0answers
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?
1
vote
0answers
14 views

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 ...
0
votes
0answers
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 ...
0
votes
0answers
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 ...
0
votes
0answers
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 ...
0
votes
0answers
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 ...
0
votes
1answer
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 ...
0
votes
0answers
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 ...
1
vote
1answer
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 ...
0
votes
0answers
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 ...
1
vote
0answers
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 ...
1
vote
1answer
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 ...
2
votes
0answers
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 ...
0
votes
0answers
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 ...
0
votes
0answers
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 ...
0
votes
0answers
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 ...
0
votes
0answers
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 + ...
0
votes
0answers
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 ...
1
vote
0answers
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; ...
1
vote
1answer
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 ...
0
votes
1answer
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 ...
0
votes
0answers
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 ...
0
votes
0answers
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 ...
2
votes
1answer
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 ...
0
votes
0answers
7 views

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 ...
0
votes
0answers
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 ...
0
votes
0answers
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 ...
3
votes
1answer
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% ...
0
votes
0answers
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: ...
0
votes
0answers
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. ...
0
votes
0answers
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
0
votes
0answers
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 ...
4
votes
0answers
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 $P \left( |X − Y | ≤ 1/6 \right)$?
1
vote
0answers
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. ...
0
votes
0answers
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 ...
0
votes
0answers
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 ...
1
vote
1answer
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% ...
0
votes
0answers
8 views

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 ...
1
vote
0answers
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 ...
0
votes
0answers
6 views

Linear time series model and z transform

I am few questions from the following papers: ...
0
votes
0answers
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 ...
0
votes
0answers
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 ...
7
votes
2answers
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 ...
0
votes
0answers
18 views

Please help me about Dunnett's test in R [on hold]

I have got a problem about the test of Dunnett's test.Why I cann't run the results. I cannot understand it.Please help me and thanks for the answer.
0
votes
0answers
4 views

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 ...
3
votes
1answer
16 views

Hypergeometric approximated Normal/Gaussian distribtuion

A large lecture theater has 270 seats, 24 of which can accomodate left-handed students. Suppose it is known that 14% of people are left-handed. One class held in the theater has 205 students. (a) ...
0
votes
0answers
12 views

Techniques for comparing two windows of data in a time series

I'm working on a small independent project in R, trying to make my own (very crude) forecasting method. The general idea of the component that is giving me trouble is trying to compare two windows of ...

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