# All Questions

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### Forecasting daily data with trend, yearly, day of the week, and moving holiday effects

I'm expanding a question I posed earlier because I think it was lacking detail. I'm attempting to forecast daily demand for a restaurant that sells take away food, primarily to office workers on ...
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### Repeated measures analysis… or not?

Not sure if dealing with repeated measures analysis...? Measuring X at 3 seasons (summer, winter, spring/fall) during a year – might be high summer/low winter, high winter/low summer, consistently ...
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### Pricing Model for desktop computers

I am trying to implement a pricing model to automatic price desktops based on some attributes(say memory, disk and brand for now). I have collected some sold history data from the internet and they ...
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### Analysis of a sample [duplicate]

I have a 10 items questionnaire (already validated) that I am trying to analyze. Respondents answered: 1. strongly disagree 2. disagree 3. neutral 4. agree 5. strongly agree. I want to measure how ...
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### Volume contribution decomposition in Log-log models

I am currently working on pricing analysis : the effect of competitor SKU pricing on the number of units sold of my SKU. The model was built on the log(units) sold. I want to measure the contribution ...
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### clumping measure

I am having to fit ellipses to multiple datasets. The input data are distance versus angle (0-180 degrees). Some data sets have a very limited range of angles, say 80-100, even though there are many ...
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### Repeated measures logistic regression

I have a dataset that features a binary outcome, a binary predictor, and an unordered factor with 7 levels, and 120 subjects. Each of the 120 subjects were asked a binary question on seven issues, ...
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### How does the proof of Rejection Sampling make sense?

I am taking a course on Monte Carlo methods and we learned the Rejection Sampling (or Accept-Reject Sampling) method in the last lecture. There are a lot of resources on the web which shows the proof ...
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### Daily Sales Data - Week Days Only, No Holidays

I'm trying to predict the daily sales for a take out restaurant. They are located in the downtown core of a large city. Their primary customers are office workers on their lunch breaks, and as such ...
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### Sizing of training and validation sets in machine learning: Is there a proven optimum, or merely heuristics?

When I watch presentations where machine learning algorithms were used, the amount of data put in the training and validation sets seems to be somewhat arbitrary. Sometimes it's 80-20, sometimes it's ...
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### Datasets for Fuzzy Clustering related with structural bioinformatics or chemoinformatics

We want to test the performance of some fuzzy clustering algorithms some collaborators have developed. Our interest lies in structural biology or chemoinformatics so we are looking for 2D datasets ...
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### Data splitting of financial time series using CARET

I am using CARET package to predict the variable Price in the financial time series , using SVM My data is like this ...
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### What are $\rho$-, $\beta$-, and $\alpha$-mixing conditions?

I have seen properties named $\rho$-, $\beta$-, and $\alpha$-mixing conditions in papers related to Copulas and Markov processes like this one: In this paper, we identify conditions on $C$ that ...
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### Precision and recall of a random classifier

My understanding of precision and recall tells me that there is a tradeoff between these two measures: you can improve one at the cost of the other. However, when I think of a random classifier (on a ...
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### Feature selection for pattern mining

I must find frequent patterns in temporal data, using a method that was imposed to me. This tool has problems handling these data: processing is long and takes a lot of memory. So, I would like to ...
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### Are the slopes of two segmented lines important in recognition of a breakpoint?

I have found one breakpoint in my linear regression but the slope of two lines have the same decreasing slope, I was wondering if the change of the slope is necessary in recognition of breakpoints.
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### How to compute the standard errors of a logistic regression's coefficients

I am using Python's scikit-learn to train and test a logistic regression. scikit-learn returns the regression's coefficients of the independent variables, but it does not provide the coefficients' ...
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### Fidelity of measurement using conditional probabilities

Let me begin by saying that I'm not entirely sure if this is the correct forum, or if Mathematics would be more suitable. The problem I'm about to describe is statistical in nature, so I suppose it ...
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### Individual sampling weights and percentages

I am working with public use microdata measuring educational attainment. I want to calculate the percentage of the population older than 25. I am merely unaware of how to use my individual weights ...
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### What factors should be considered while spec'ing a system for R install [on hold]

I am putting together [hardware/workstation] specs for installing R statistical software and I cannot seem to find the factors that I should consider for this. Specifically, if I know the ballpark ...
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### Dummy variables in SAS Enterprise Miner

When I modify my dataset to include dummies, how then are those variables to be treated as? As a binary or interval variable? I would be glad for an answer from a person who is sure about that. I ...
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### Correlation between a categorical predictor and a continuous outcome variable

How do I perform correlation between a categorical antecedent variable and a continuous outcome variable? Like for example, correlating EACH attachment style with another variable, i.e, social ...
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### Function MATLAB eig last component is incorrect [duplicate]

I am trying to write a PCA function in MATLAB. I know that there is the function princomp, I just wanted to understand the process for myself. One problem I've encountered is that the eig matrix ...
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### Coefficients and Categorical Variables

Suppose that a categorical variable $X$ can take three values: $0$,$1$ or $2$. If we run a Cox proportional hazards model and get an estimate of $\beta_1$, how would we interpret this? So we get: ...
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### Implementation of prototype selection in application to nearest neighbor classifier

I am looking for an implementation of prototype selection algorithm and it is highly preferable that implementation would be in Python. I am using sikit-learn, but there is none.
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### How to do multiple treatment meta-analysis?

I would like to compare 3 different treatments (no one treatment is considered the placebo, and these are not randomized control trials) from multiple studies in a meta-analysis. I am using the ...
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### Why does the STD not decrease when I do more measurements?

I made 100 measurements of a certain quantity, calculated mean and std (with MySQL), and got mean=0.58, std=0.34. The std seemed too high relative to the mean, so I made 1000 measurements. This time ...
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### Whether to chi squared or not to

I have an extremely large data set, but I'll simplify it down as, although I think I should use a chi squared test, I've run into difficulties applying it: Let's say I have a list of 20 different ...
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### Selecting genes more affected in treatment A than treatment B

We are trying to test the hypothesis that a mild mutation of a gene has few effects on the expression of the transcriptome than complete deletion. Further we wish to test the hypothesis that the genes ...
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### comparing gam model with different length data

Consider the following example: ...
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### Using LDA in non-realtime twitter data

I try to understand user characterization from twitter data. How can I understand the user's interest from statuses? From my researches, LDA(Latent Dirichlet Allocation)suitable for topic extraction. ...
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### Marginal effect of squared variable in Probit Model

I want to estimate the following probit model $employed_t=\beta_1 age + \beta_2 age^2$ and I use the Stata code probit employed c.age##c.age Using the command ...
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### Modeling data with logistic regression

I am new in statistical modeling and l am trying to model a financial data with logistic regression and I am facing a challenge here. Some of the predictor variables have integer values( negative, ...
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### Assessing quality of a fixed sample size with limited information about full set

Given the level of this site these are probably intolerably newbie questions, but here goes... So I'm studying the cost of public transport in a given city. I have access to data from a hopefully ...
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### Recoding a variable with three levels into a dummy variable

I need to recode the variable school setting (urban, sub-urban and rural settings) into a dummy variable. I know that when creating a dummy variable, there is one category less (so 2 rather than three ...