Tagged Questions

A statistical model is a formalization of relationships between variables in the form of mathematical equations. The model is statistical as the variables are not deterministically but stochastically related.

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1answer
19 views

How do models, parameters, specifications, restrictions and assumptions relate?

So this has been something I've been struggling with for a long time: The specification of a particular model is subjective. However, there seems to be objective ('true') values of the parameters we ...
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0answers
20 views

Transformations in Simple Linear Regression [duplicate]

Suppose a linear model for Y in a single predictor var, X. If the residuals show a pattern of increasing variance (wrt X), sometimes a transformation of Y, Y'=f(Y) is considered (where f is sq rt, ...
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0answers
9 views

Assumptions on a multiple linear regression model and elastic net

I am interested in using elastic net regression in place of an multiple linear regression. I know when you perform a multiple linear regression you should check the assumptions such making sure the ...
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0answers
20 views

How to choose the best regression model?

I have entered main effect terms in Block 1 and interaction terms in Block 2. Based on their beta values, the main effect terms were not significant in Block 1 and the interaction terms were not ...
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0answers
21 views

How can I assess if a parametric model can reproduce the same curve with different parameters?

I have a parametric model that I think it is "degenerate" in the sense that I can obtain the same model with different parameters. For example, if I have a convolution of two 1D Gaussians (say, G1 ...
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2answers
244 views

Was this the appropriate regression model?

I was recently proof-reading a friend's thesis (for their writing, not stats usage) when I came across a usage of a regression model which I would regard as incorrect. However, I'm pretty new to the ...
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0answers
7 views

Linear model for RCBD

Hi i am told to write a linear model for my stats assignment under an RCBD. ...
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0answers
19 views

Do assumptions for estimators affect population parameters?

TL;DR: Specifying a model (a collection of restrictions over a sample space) specifies the model parameters. Specifying an estimation procedure adds additional number of restrictions (assumptions?). ...
2
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1answer
12 views

Repeated measures - sum of biomassproduction

I am student in biology. For my examination I conducted a greenhouse experiment with gras. Actually I am not sure how to develop the correct model and unfortunately I haven't found an answer in the ...
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0answers
22 views

Fitting a model to data for prediction - best choice for data

I have some data I need to fit a model to that can be used for prediction (interpolation). The data is summarized by the plot below. The black line is x=y. I want to be able to fit a model so as I ...
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0answers
16 views

Model Averaging

Good Afternoon, I am working on model averaging of data collected about bird species and habitat vegetation. I have been using the MuMIn package in R and have taken a subset of all possible models ...
6
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1answer
414 views

Why should we use t errors instead of normal errors?

In this blog post by Andrew Gelman, there is the following passage: The Bayesian models of 50 years ago seem hopelessly simple (except, of course, for simple problems), and I expect the Bayesian ...
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5 views

given a set of pairs of graphs, build a model that accept a graph and predicts it matching graph

Training Data I have a set of pairs of normally distributed graphs, each with a concrete last sample (maximal X) Question I want to build a model (formula) from the data input: a single graph ...
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0answers
30 views

How to interpret ANOVA output comparing two models

I'm working with the Blackmoor data from the study "Female adolescents with anorexia nervosa and their parents." I've made 4 models based on this: ...
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0answers
33 views

Reverse engineer a predictive model from a time series graph

I have found some real estate plots in a scientific article. These graphs mainly describe, the believes of the author of the development of the real estate market in the future for certain countries. ...
2
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1answer
43 views

Correct numerical result in Bayesian model comparison

I was wondering how to calculate the following Bayesian model comparison. Suppose you have a couple of models: $$M_{1}: x \sim Bin(n, \pi); p \sim Be(1,1)$$ $$M_{2}: x \sim Bin(n, \pi); p \sim ...
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0answers
10 views

How to take care of the percentage/rate of an absolute number as independent variable?

I am working on a mixed model, where suppose I have several stores of different sizes. The number of products manufactured in each store is different, say one store can manufacture 100 and other can ...
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1answer
24 views

Definition of Parameters [duplicate]

I imagine this either extremely simple or extremely complex. I am trying to understand the interpretation of the term 'parameter'. A couple of quick online searches deliver an intuitive understanding ...
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0answers
10 views

Comparing goodness-of-fit across conditions

I have repeated-measures data. Participants complete both Stage A and Stage B (random ordering). I have two complex models, Model 1 and Model 2, which are fit using optimization techniques. Model 2 is ...
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0answers
19 views

Model functions of Bates and Watts?

Bates and Watts (1988) is often referred in my lecture notes of nonlinear regression. Does their book include some sort of list of basic exponential and logarithmic model functions. Simple ...
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0answers
15 views

How to measure classification accuracy based on presence only data?

I have a binomial GLMM which I calibrated with data on recreational visits (presence) compared with random controls where no visits were recorded (absence). I generated the controls myself, whereas ...
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1answer
27 views

Goodness of fit: observed vs simulated data

I have a set of 2-dimensional "observed" data of sample size N: $$O = \{(x_1, y_1), (x_2, y_2), ..., (x_N, y_N)\}$$ The hypothesis is that $O$ is a realization of ...
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0answers
14 views

How can I validate if a pattern is meaningful?

I am a financial analyst for a construction company. My goal is to develop an accurate sales model that is correctly reflects prior sales history (back testing) so I can then predict future sales. I ...
1
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1answer
17 views

Correct application of linear regression models from different types of features

I want to build a predictive model of a value which changes over time from features which can be partitioned into 2 types - 9 features which describe the history of the value (And could be used to ...
1
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1answer
32 views

Assessing residuals from a regression model

I am trying to understand what the residuals from a regression convey about the model's adequacy/ability to explain the variance in the data. I read that if we are able to take the residuals from a ...
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0answers
13 views

How to model data

I am attempting to model a specific variable's sensitivity to a feature set. In concrete terms, I am trying to predict the duration (PAUSE_KS) of a letter (...
1
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1answer
144 views

What if the trend is changed?

I want to forecast tourist arrivals using time series analysis. I expected to use monthly data from 2000-2013. But due to the civil war, the trend was changed after 2008 as in the following plot. ...
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1answer
20 views

Percentage Beyond a Given Value for Empirically Defined Distribution

It is my understanding that standard deviation does not work well as a measurement for distributions that are heavily skewed. If I have a heavily right-skewed distribution, should I simply use the ...
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1answer
11 views

What method should I use to model simplified performance

I have the data of some build times. These builds occur on a cloud and the runtime has been more varied than in the past. One thing that could be occurring is an improper sharing of resources ...
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1answer
25 views

R- predict payment day (1-31)

I need to predict payment day of the month (1-31) for each client (I have at most 9 month of payments and on average is 5). I have both categorical variables and numerical. I tried to use rpart to do ...
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3answers
67 views

backward selection multivariate analysis usind R

I want to perform an exploratory Cox regression analysis of medical data using R. I am practicing using the pbc data from the survival function. How would you recommand performing a backward ...
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0answers
10 views

Managing/maintaining multiple models

Sorry for posting a vague problem statement, but this is very practical issue i am facing right now and couldn't any hint/solution. My use case is that while trying to build regression model, there ...
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0answers
18 views

Fitting data in multivariate Gaussian

I have a dataset of N*d feature vectors and I was asked to fit them in a multivariate gaussian, with a matlab function (that someone else has programed) that recieves the number of points, mean and ...
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2answers
74 views

Rate of change for the regression model $Y^{\frac{1}{2}}=a+b_1*log(X_1)+b_2*X_2^{\frac{1}{2}}$

Hello I have the regression model $Y^{\frac{1}{2}}=a+b_1*log(X_1)+b_2*X_2^{\frac{1}{2}}$ which works very well however I am trying to interpret it in terms of change for each different $X_i$ term. I ...
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1answer
37 views

Saving each step of Backward selection in R

I'm trying to recreate Leo Breiman's work http://www.stat.washington.edu/courses/stat527/s13/readings/BreimanSpector_1992.pdf and I'm experiencing some major difficulties in R. I've made it that far ...
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0answers
5 views

Calibrating a model using different timesteps, mean/skew

Suppose I have 1 year of hourly streamflow values - approx. 8760 values. I am developing a model that outputs an estimated streamflow value for each of the 8760 values. I examine the sum of squared ...
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0answers
33 views

data retrieval vs modeling

i don't have a specific mathematical setting for this question. it's rather high level. if you have a bunch of data X for a variable that we want to predict Y, and all we care about is predicting ...
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0answers
48 views

Identifying What Causes a Variable to Increase

Say I have a dataset with several continuous and categorical variables, and I want to identify what variables (values or properties of these variables) may cause one of the continuous variables to ...
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0answers
23 views

Interpreting R results, are the data multivariate normal?

I ran "mvn" using the "mclust" package in R using the following codes: mvn("EEE", data[,18:22], prior = NULL, warn= NULL) I am having trouble figuring out how to ...
3
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1answer
64 views

What kind of model can I try to fit in this plot?

I have a plot like this. I wish to apply a model to this, however, I guess a linear regression model won't work on this. What I did was plot it on logarithm x and logarithm y axis as well but it ...
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4answers
80 views

Evaluating performance of machine learning models

I'm trying to predict when a location has enough wind to go sailing. I've built several models that look for correlations between different weather conditions and whether it ends up being windy X ...
2
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1answer
33 views

Is it acceptable to not include high-order interactions (3-way and above) in the model when they are not by themselves of interest?

Is it acceptable to not include high-order interactions (3-way and above) in the model when they are not of interest and not part of the hypothesis that is being tested? NB. I am not talking about ...
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0answers
15 views

What are possible theories/models to describe social influence based on frequency?

I am working on social influence based on frequency, meaning if a person repeatedly appears at a location many times then he/she is more influential at that location. In other words, he/she can ...
0
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1answer
26 views

Determining if time has influence on correlation between x and y

Is there a sort of statistics model I could use to determine if time has an influence on the correlation between two sets of data? For example say I have a column $X$ and a column $Y$, both just ...
1
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1answer
23 views

Estimating costs with extreme values

I am trying to estimate health care costs and I was wondering what the standard practice is for extreme values? By extreme values I mean I have a large portion of my costs being zero and a small ...
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0answers
31 views

How to correctly choose model based on BIC?

I have a question about Bayesian Information Criteria. (GARCH models) I have looked for so many hours but still very confused about this BIC especially a negative one. As far as I am concerned it is ...
0
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1answer
47 views

Interaction model significant in multiple linear regression

This question is not about interaction effect, but about interaction model in Hierarchical Linear Regression. I have 1 DV and 5 IVs. I want to see which of the IVs is significant predictor of DV. ...
0
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1answer
29 views

Clustering Two Variables With Disease Information

I was proposed a problem and I am not quite sure how to go about it. The problem is I want to find a relationship between two variables. For the simplified case there are only two variables, lets say ...
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0answers
13 views

Variables occurring after target occurence, can they be used in regression model?

My study is to judge the appropriateness of target=1, not for predictive purpose. Can the variables occurring after target occurrence be used in regression or decision tree model? For example, a ...
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1answer
25 views

Which is better ROC curve or Confusion matrix?

anyone know about the predictive model evaluation? I'm confused about the ROC curve and confusion matrix. The area under the curve for ROC is represent about the accuracy of the classifier. But what ...