# All Questions

7 views

### What kind of distribution is this via t-distribution

Suppose we repeat an experiment identically and independently 100 times. Each time we construct a 99% conﬁdence interval for $\mu$ via the t-distribution. Let X = the number of times the conﬁdence ...
4 views

### Inference with only left-censored data

Suppose I have a data set that is only left-censored data, ex: <5, <5, <5, <10, <10, <10 A technique to handle left-censored data is the Kaplan Meier estimate, see page 5 of ...
13 views

### Not sure I understand how R calculates the covariance

Please forgive this silly question, I'm fairly new to statistics. Consider this R code: ...
7 views

### Does the estimated overdispersion parameter of Negative Binomial depend on mean

Negative Binomial distribution can be parameterized using mean, $\mu$, and overdispersion $\psi$, so that the variance of NB is $\mu + \frac{\mu^2}{\psi}$. We know there is no analytical solution for ...
71 views

### Problem with evaluating if a 2D or 3D point lies in a Gaussian sphere (for implementing a Parzen-window estimation)?

START EDIT I try to formulate it more briefly: I have 2D or 3D sample points in a coordinate system, and want to check which of those points lie within a (bivariate/multivariate) Gaussian ...
9 views

### JAGS meta-analysis

I'm using JAGS to run a meta-analysis and I've run into an issue. I have calculated log-response ratios and errors for about 177 studies, where studies fall into one of 8 groups. I'm interested in ...
20 views

### Hierarchical Bayesian modeling of incidence rates

Kevin Murphy's book discusses a classical Hierarchical Bayesian problem (originally discussed in Johnson and Albert, 1999, p24): Suppose that we are trying to ...
18 views

### Finding an equation with many variables to fit a set of data

I am writing a program which takes notes from a keyboard as the input, (just numbers, 1 to 88) and decides which notes are played by which hand. There are a lot of variables, for example, the position ...
15 views

### How to subset alternatives in nested multinomial logistic regression?

I am trying to predict whether or not captains in a particular groundfish fishery choose to fish on any given day and what variables may influence that decision. Originally I had planned on using ...
16 views

### SVM for unbalanced data

I want to attempt to use Support Vector Machines (SVMs) on my dataset. Before I attempt the problem though, I was warned that SVMs dont perform well on extremely unbalanced data. In my case, I can ...
52 views

### Why we shouldn't be obsessed with unbiasedness

In my Bayesian statistics class, my professor makes the remark that we should not be obsessed with unbiased estimator. First: I understand this statement in the sense of trading biasedness for ...
11 views

29 views

### Identifiability in linear regression

If we have a generative model: $X_2=X_1a_1+\varepsilon$, where $\varepsilon \sim \mathcal{N}(0,\sigma_2^2)$, do we have $X_1=X_2a_2+\varepsilon '$, where $\varepsilon \sim \mathcal{N}(0,\sigma_1^2)$ ...
68 views

### What does the | in |Z| mean in mathematical expressions for distribution statistics

I am doing some self study on statistics and noticed that in the notes that I was using the $|Z|$ expression as attached in the photos below. I am confused with the "$|$" that is being used. The only ...
8 views

### which test to use here to test the significance of overlap with respect to a control?

i'm not sure what statistical test to use to compare a scenario like this: I have a list of candidate regions A (560k regions) and I want to know if my candidate regions enrich for a particular set ...
32 views

### What to do with missing values?

I have missing values for some of the variables in my data. I am using pooled OLS and have 144 observations. I have missing values for three of the variables. Less than 10% of the data for each ...
20 views

### R packages that work with biased samples

I'm working with a biased sample of web users. I'm only able to track responses of users who have navigated my site in a certain way, and I'd like to run an analysis to determine how certain factors ...
8 views

### Labelling subplots [on hold]

I have produced a volcano plot, however for an examples sake, let's use : ...
5 views

### How to integrate observational errors in goodness of fit tests?

I have an astrophysical non-linear curve, specifically a power spectrum. I need to fit this curve with a model and obtain the goodness-of-fit (GOF). This gives me expected and observed values. The ...
30 views

### How does this algebraic relationship among expectations work?

Find the expected mean squares error of lack of fit. Trial: $$SSLOF=\sum_{1}^mn_i(\bar y_i-\hat y_i)^2\\=\sum_{1}^mn_i(\bar y_i-\bar y)^2-\sum_{1}^mn_i \hat\beta_i^2(x_i-\bar x)^2$$ and ...
12 views

### Repeated measures tests without “before and after” measurements

When reading about repeated measures ANOVA, until now 99% of examples are always with "before" and "after". But if I understood correctly the point of repeated measures ANOVA is not necessarily to ...
5 views

### Evaluate deviation from negative binomial model

I'm trying to figure out how to determine to what extent a sample deviates from a negative binomial model fitted to a larger population. As an example, I generated counts of doctor visits for a ...
5 views

### how to measure multichannel distances between “event” sequences

In TraMineR, seqdistmc is used to measure multichannel distances between "state" sequences. I am wondering if there is a function to measure multichannel distances between "event" sequences.
21 views

### Cox PH model selection and validation

I am trying to analyze my data using survival CoX PH in SPSS v.19 and also attempting to make different prediction models (without and with a biomarker of interest). I am a clinician (not a ...
10 views

### How to can IRT-Models be understood in GLM/ SEM Framework? (Predict Learning with added Paradata-Covariates)

I'll be working with data from an a Intelligent Tutor System similar to one studied in the KDD-Cup 2010 on Student Performance Prediction and plan to use IRT-Models to infer item and ability ...
22 views

### Cluster with distance threshold in R

I'd like to get clusters with a maximum inner distance threshold. Now I use hc <- hclust(d) and cutree(hc, numofclasses). ...
33 views

### Maximum Likelihood Estimation with Known Parameter Distribution

Consider i.i.d observation vector ${\bf x}$ from a distribution $F$ depending on vector of parameters $\boldsymbol{\theta}$ and single parameter $\alpha$. We would like to estimate parameters ...
18 views

### Adjusting significance level with for different kinds of tests (chisq, mann whitney etc.) on the same variable

I have conducted a series of tests on a single, dichotomic variable (presence/absence of a personality disorder in a neurological illness) in order to compare several things (i.e. presence of anxiety ...
32 views

### AR(1) on autocorrelated data that is not a time-series

I need to apply a regression model on observations that is not time series data but each observation presents a store and the amount of cartons that gets sent to that store. For instance ...
10 views

### Relationship between number of Principal components and Exploratory factors.

Would like to know is there any heuristic relationship between the number of components identified from PCA analysis and the number of hidden factors provided by EFA analysis on the same data set?
39 views

### How to model a skewed Student's t disribution

I have a small number of samples (5) of a large population (~10,000). The samples are percentages and hence I know from the context that no answers are possible below 0% or above 100%. From this one ...
25 views

### Hammersley–Clifford theorem

I'm reading this paper http://image.diku.dk/igel/paper/AItRBM-proof.pdf and I got stuck in page 4 with equation (1) that's based on Hammersley–Clifford theorem. I'm not good in reading set theory ...
12 views

...
11 views

### Difference in memory usage between gbm and blackboost [migrated]

I'm working on a database with around 250000 observation and 50 predictors (some are factors so in the end around 100 features) and I have trouble using the blackboost() function (from mboost package) ...
19 views

### Is it ok to adjust significance level according to number of comparisons in simple correlations?

a referee asked me to "split" the significance level for the number of comparison, although i am not doing repeated comparisons but just spearman correlations between variables. I have set the ...
6 views

### Model selection and parameter estimation in forecasting with a Dynamic Linear Model

I am implementing a general purpose prediction tool for time series. I want to tolerate missing values, so I decided to settle for DLMs. To make it as relevant as possible on a large number of ...
14 views

### Standard deviation of normalized data

I have a data set $y_i$ with the standard deviation $\sigma(y_i)$ for each value. The $y_i$ represent some value of photon count rate. For some reason, I normalize the data set to the average count ...