# All Questions

34 views

### Understanding Naive and Multivariate Gaussian Classifier

Thank you for checking this question out. I am trying to understand how to use the multivariate gaussian classifier. To introduce you better to my problem, I will show how currently I classify data. ...
8 views

### Matlab: finding coefficients of ODE system

I have all the data and an ODE system of three equations which has 9 unknown coefficients (a1, a2,..., a9). ...
28 views

### multiple regression and multiple comparisons

Say I fit a multiple regression of p explanatory variables. The t-test will allow me to check if any single one of those is significant ($H_0: \beta_i = 0$). I can do a partial F-test to check if some ...
18 views

### R package nnet - neural network question

I am experimenting with neural network package in R nnet and i have some questions. The regulatory environment i am working on requires me to reproduce my results to show them to the auditors. How ...
17 views

### Easy-to-apply tests for randomness

I'm interested in testing a sequence of numbers for randomness. I've done some searching and come across die hard and die harder. However these tests seem to require a *nix platform and quite a bit of ...
21 views

### Bootstrapping to find confidence intervals. Very small sample size

I am trying to generate confidence intervals for estimates of numbers of fish observed with a very small number of surveys. Most of the numbers of fish observed are very small as well. The estimate ...
13 views

### Regular Conditional Bayesian Experiment

In "Elements of Bayesian Statistics" (1990), Florens, Mouchart and Rolin describe two basic forms of reduction of a Bayesian experiment: Marginalization and Conditioning (Ch. 1). I don't understand ...
11 views

### Which variable vary previously to the other one

Here are two variable (a and b) and their value through time (time.a, time.b) ...
26 views

### Categorical vs Continuous Variable

I have two variables, one continuous and one categorical which I currently both use as predictor variables in a logistic regression model. Their relationship is shown in the following plot with the ...
29 views

### Which variables have too much variation?

So I have 1000 variables (different lakes), each with 12 observations (each lake was tested once a year for 12 years). Some of the lakes are really small, so we think they have way too much variation. ...
14 views

### Mallows distance hypothesis test: p-value =?

I am using Mallow's Distance (normalized Earth Mover's Distance) to characterize the similarity between two histograms. This is working very well, but I would like to identify a specific cut-off where ...
7 views

### Decision trees partitioning predictors?

In general, decision trees such as CART represent row-wise (or record-wise) partitions of training data. I wonder if there is any recursive method partitioning data in column-wise (predictor-wise) as ...
17 views

### Value at Dmax from Kolmogorov-Smirnov Test in R

I am comparing two distributions using the Kolmogorov-Smirnov test [ks.test()] in R and would like to know what the numerical value is where Dmax occurs. It's not in the output of ks.test() as far as ...
10 views

### Sorting/Clustering similarity matrices

I wonder, what are the available libraries in R or Python to do correlation matrix clustering (sometimes it is referred to clustering). I also, wonder, after clustering/grouping each point. What is ...
16 views

### cumulative distribution function plotting [duplicate]

I have some values from different repetitions of different experiments and I need to plot cumulative distribution function. You can see a fraction of my file below. can you help me how can i do that. ...
40 views

### Correlation vs measure of independence

So I have some data of which I'm looking at two different metrics, the first being "how sick a person is (higher = sicker)", and the second being "the presence of adverse events", and I've run 20 ...
31 views

### What is the difference between the F-test and the Wald / Likelihood Ratio / Score tests of linear models?

In statistical inference, it's common that investigators will report the results from Wald tests for simple univariate inference or likelihood ratio tests for nested models. However, in regression ...
20 views

### What does it mean to correlate residuals in SEM?

I have been reading a paper by Cole, Ciesla, and Steiger, which argues in many cases allowing residuals to correlate is justified. However, I am not entirely sure what it means for residuals to ...
17 views

### calculating CDF for different run extrated from a text file

I have a text file with four columns as below. the first column shows the name of experiment, second column shows the number of repetition (because each experiments is repeated for example 10 times), ...
39 views

### How to choose the test statistic for permutation test?

Is the purpose of permutation test to test the null that several groups of samples come from the same distribution? I found its steps are The steps in a permutation-based computation of the ...
32 views

### Independence of samples

Recently I started doing verification on daily temperature forecasts by different providers. I calculated the absolute forecast errors for each of the providers, and I am planning on performing ANOVA ...
28 views

### How do you prepare longitudinal data for survival analysis?

I'm trying to plot a Kaplan-Meier curve of my data with R. Currently, the data is in the following format: ...
39 views

### How to reshape a variable to, say, mean = 5, sd = 10? [duplicate]

The problem I am having is that I have a distribution that I want to remain the same shape, but the mean and variance altered. When I use scale() in R, it can ...
207 views

### Test accuracy higher than training. How to interpret?

A ML newbie here. I've a dataset containing at most 150 examples (splitted to training & test), with many features (higher than 1000). I need to compare classifiers and feature selection methods ...
16 views

### Formula for computing variable from Likert-type scale

I have this model: $$4F + 4.8N = a + bM +cP + dH$$ where $F$, $N$, $M$, $P$, $H$ are variables measured on a 7-point Likert's type scale and $b, c, d$, are coefficients and $a$ is a constant. I am ...
14 views

### Categorical value “stuck” during sampling of my model

I'm having some troubles with the implementation in pyMC of my probabilistic model. Note: you can skip directly to the code section, if you're not interested on the use of the model. The model ...
28 views

### How to compare Likert scale items before and after an intervention?

I have been struggling with this question all day, reading everything I could find, but still do not have a clear answer. A part of my research was that: 30 students tried a new educational ...
41 views

### How to adjust the shape of a gamma distribution

I have a dataset (vector) to which I would like to fit a gamma distribution (x), which given the shape seems reasonable. The charts below show the histograms of the two dataset: vector and x. The ...
18 views

### Selecting tuning parameters with caret using standard deviation of custom metric

I'm using caret with custom fitting metric, but I need to maximize not just this metric but lower bound of it's confidence interval. So I'd like to maximize something like ...
47 views

### How to implement this maximum likelihood algorithm?

I have a log-likelihood function $$l(b) = \sum_{i=1}^n \left( \log(b_0 + b_1 x_i + b_2 x_i^2) \right) - \sum_{i=1}^{n+k} \left( \int_a^{x_i}\exp(b_0 + b_1u + b_2u^2 + b_3 u^3) du \right)$$ For ...
28 views

### How can I visualise a distribution that is univariate normal but bivariate non-normal?

I used the MATLAB code written below to create the following probability density function. It creates the familiar hill-shaped distribution. I'm interested to see (whether via MATLAB code or just ...
9 views

### Using ANOSIM to analyze randomized complete block design data?

I've used NMDS to explore data collected in a randomized block design, involving three treatments, each applied in 10 spatial unit blocks. Is it possible to use ANOSIM to test for hypotheses of ...
12 views

### Does it make sense to minimize negative log likelihood on SVC probability outputs

I'd like to run a grid search cross-validation on the probability outputs of the SVC classifier. In particular I'd like to minimize the negative log likelihood. Is this a reasonable thing to do? I'm ...
32 views

### Why does latent variable modelling in regression tend to push R Squared up?

Hypothetically, say I have I have three manifest variables measuring anxiety and three manifest variables (items) measuring stress. Then I want to use both to predict scores on depression, which I'm ...
17 views

### Fixed Effects Regression with Interaction Term Causes Error

I am trying to estimate a panel dataset with an interaction term for geographical areas (LoadArea, DischargeArea) which signifies a route. Using the fixed effects specification, it does not like the ...
31 views

### Transformation of leptokurtic data

I'm working on my BSc dissertation currently. One of my variables is created using the ratio of one continuous (mostly) normally distributed variable to another. The distribution of ratio is very ...
32 views

### Is my random variable affecting my response?

I performed an experiment on coral colonies (10 colonies, randomly chosen in repeated measurements); manipulating aragonite/carbon chemistry and temperature (fixed effect) to analyse effects on the ...
37 views

Okay, this might seem like a stupid question and it sure feels that way. And I have probably just lost myself by overthinking it or something, but here goes: In Cohrans C-test you take the ratio ...
11 views

### 3x2x3 ANOVA with repeated measures

I am a beginner of statistical analysis. Currently I am using SPSS software statistical package. How to perform repeated measures ANOVA for the following data: 5 emotional states x 2 hemispheres x 5 ...
12 views

### Estimating the disequilibrium error in ECM

I am supposed to estimate the labour market disequilibrium for my master thesis. I am using an error correction model specification for the federal states in Germany. I am using labour (emp), gdp, ...
14 views

### marginal effect clogit not significant

I developed a coniditional logit model on STATA, the model is good and the variables are highly significant Then I do mfx predicted (PU0) to determine the marginal effects of variables (dy / dx). the ...
70 views

### When does replication reveal fraud?

Found this question here, and I couldn't answser it and thought it would be a wonderful question for this site. Here's a little thought experiment for your weekend pleasure. Consider the ...
29 views

### How do I analyse a two-alternative forced choice test?

I have recently as part of my bachelor project at my university conducted a two-alternative forced choice test. I have looked at ways to say something with significance about which images (the test ...
36 views

### Probability distributions

What is the probability that a random number [0,1) will lie in [0.5,0.6]? As far as I know, there are 3 probability distributions in physics we usually use, but I am not sure when we can use ...
35 views

### How does SVM prediction work?

As far as I understand, the training phase usually uses the dual optimization formulation where we can implicitly calculate the weight vector which defines the discriminant function. How about the ...
23 views

### Simple mean reversion measure for binary time series

I am trying to define a simple measure for mean reversion in a stochastic sequence of ones and zeros, which I denote by $x_t$. Yes, a unit root test on the cumulative sum could be a viable choice, ...
46 views

### What is endogeneity and what does it mean substantively? As an extension what is exogeneity?

My apologies if this is an obtuse question, I am neither a statistician nor a econometrician but as a student is empirical methods this question plagues me. I understand that $$X'\epsilon=0$$ not ...
23 views

### How to score the options in a questionnaire and develop a scoring range in a risk profiler questionnaire?

I have developed a risk profiler questionnaire but don't know how to score the options and make a scoring range. Once the range is developed, I could categorize the client as conservative, moderate ...
45 views

### Simulating multiple linear regression

I would like to simulate a multiple linear regression model using R. If I have the skewness and kurtosis for the residuals, how can I do that?
60 views

### Why are log transforms used in measuring dose-time association?

Explain why log(dose) and log(time) are used to measure the association between dose and time instead of the actual values of dose and time.

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