# All Questions

3 views

### Generating ace.arff for WEKA [on hold]

i used hex editor to unpack a set of malware but am having problem in converting it into arff so it can be classified with WEKA
47 views

### Why can't the chi squared test be calculated with a row of zeros?

I have some trouble to calculate chi squared statistic with R. My data and code are: ...
23 views

### Intuitive descriptive statistics for power law distributions

For normal distributions we have a set of intuitive descriptive statistics that help us understand how a variable is distributed (mean, mode, median, standard deviation, skewness, & kurtosis). ...
8 views

### System failure data - normalize data when there is more data available for that system

Suppose I have the following data from 6 systems. The number of Type A systems is 2 in 6 so 1/3. There are 2/3 of B systems. In the 6 systems there were 40 failures in total. ...
53 views

### Definition and proof of Strict Stationarity

The definition of strict stationarity I'm using is the following: $(X_1,...,X_n)=^d(X_{1+h},...,X_{n+h})$, for any integer h, and positive integer n. I'm trying to prove that ...
21 views

### From Identification to Estimation

I'm currently reading Pearl's piece (Pearl, 2009, 2nd edition) on causality and struggle to establish the link between nonparametric identification of a model and actual estimation. Unfortunately, ...
16 views

### A union bound on a continuous variable

Assume a continuous point process (say Poisson) in [0,t]. Assume that it is given that only three jumps occurred in [0,t], however, their exact time coordinate is unknown. In addition, it is known ...
62 views

### Why are mixed data a problem for euclidean-based clustering algorithms?

Most classical clustering and dimensionality reduction algorithms (hierarchical clustering, principal component analysis, k-means, self-organizing maps...) are designed specifically for numeric data, ...
19 views

I have a silly question about EFA. Can EFA be used to identify latent variables in a research design where multiple raters used the same rubric for various essays? Say, using the same rubric, the 1st ...
23 views

### How to standardized my data

I require to standardize my data before conducting any statistical tests, but I don't know how to do it or what procedure would be more appropriate. I am running a number of statistical tests to test ...
16 views

### Correlation coefficient significance based on bootstrap distribution

There is data $x$ and $y$ which does not come from two dimensional normal distribution. However I would like to perform correlation coefficient test. For this purpose I have created the bootstrap ...
357 views

### Using years when calculating linear regression?

I'm new to statistics, and I'm currently trying to solve an assignment for my course. The assignment is to calculate the linear regression analysis/regression equation for a data set containing ...
23 views

### How to check if people think 3 is a lucky number while we throw with 2 dice

On the marketplace Gypsy accepts bets on two dice throw (he throws two dice at the same time, not one after another). Gamblers come and say what numbers will be on each of the two dice (it is a bet on ...
21 views

### SPSS 16 goes off when i try to create a pie chart [on hold]

When I try to create a pie chart SPSS 16 closes after selecting "summaries for groups" and clicking on "define". What am I to do?
40 views

### sum of truncated normal with two normal distributions

Suppose I have one normal distribution $W \sim N(\mu_{w},\sigma_{w}^2)$ with a known cuttoff point (percentile) on this distribution called c. The first part of $W \in [-\infty,c[$ needs to be ...
13 views

### Creating a treatment group to measure uplift in sales for an advertising campaign

I have sales by state and week. Alabama|Alaska|Arizona|... 231|139|277|... 256|154|307|... 267|160|320|... 256|154|307|... 267|160|320|... I need to create a treatment group that bunches up the ...
17 views

I am trying to apply Factor Analysis to a dataset with about 200 datapoints and 8 variables. When setting the n_components parameter to 8, I get a loading matrix with loadings for three factors that ...
201 views

### When should I apply feature scaling for my data

I started a discussion with a collague of mine and we started to wonder, when should one apply feature normalization / scaling to the data? Lets say that we have a set of features with some of the ...
26 views

### How to obtain index of a vector? [on hold]

This should be a quick question, but I've been stuck on it for quite some time... I was using the function predict in R package "rpart", and the function returns a vector that looks like below: ...
35 views

### Why AUC-PR increases when the number of positives increase?

I asked a question earlier about comparing models using Precision-Recall AUC. One of the answers included the following statement: "The larger the fraction of positives in the data set, the larger the ...
18 views

### auto.arima and Arima (forecast package)

I am facing a strange issue with auto.arima. On a dataset named data, I run the following code ...
162 views

### Problem interpreting the Beta distribution

On p38 of Lee and Wagenmakers (2012) "Bayesian Cognitive Modeling: A Practical Course" the following passage appears: "One of the nice properties of using the θ ~ Beta (α,β) prior distribution ...
13 views

### Negative binomial instead of ordinal logistic?

I have data with one metric and a discrete outcome that I'm trying to estimate the probability of. The outcome is a count, but it's a safe assumption that the increments aren't i.i.d. I thought an ...
52 views

### What are some useful robust and scalable approaches towards anomaly detection of a time series data?

What are some useful robust and scalable approaches/methods towards anomaly detection of a time series data? I am mainly looking for some practical approaches carried out using Python, R, Java, etc. ...
26 views

### Does it mean anything when all items load negatively on one factor when several factors are output?

So I am fairly familiar with factor analysis, and am aware of answers here and here that tangentially address my question. I believe I am right in my answer to the question I'm asking, but I wanted to ...
6 views

### Power Law Effect with Pitman-Yor Process

I know about PYP and that they produce power law effect and am looking at some of the graphs, like: http://deliveryimages.acm.org/10.1145/1900000/1897842/figs/f1.jpg and wondering how would you draw ...
64 views

### Exponential random variable

The time it takes a printer to print a job is an exponential random variable with mean of 10 seconds. You send a job to the printer at 9:00 am, and it appears to be the fourth in line. What is the ...
17 views

### How do I read in columns from a file with R [migrated]

I have files of the following format (just numbers, nothing else): ...
9 views

### Can ANCOVA be used to control for lengths of treatment?

I have the same treatment I administered to two groups (experimentals and controls). (This is a hypothetical study asked by one of my students.) The experimental group received the treatment for 6 ...
46 views

### Comparison of machine learning algorithms

Suppose i have taken 8 machine learning algorithm which is used researchers more frequently.I have applied these 8 machine learning algorithm over 8 datasets which is publickly available on internet. ...
51 views

### How to quickly identify participants responding randomly to self-report psychometric tests with many items?

Many psychological studies involve getting participants to answer a hundred or more closed ended questions. A standard context would be a personality test with 100 items where each item is answered on ...
8 views

### Citation for IV coefficient sign change with inclusion of interaction term

I have a two step regression model where I entered my three IVs in step 1 and one interaction in step 2. One of the IVs in the interaction has a positive coefficient in the first step and then a ...
31 views

### Interaction between a dummy variable and a variable with a quadratic form

I am finishing up an econometrics assignment and this problem has me stuck. I have estimated a regression equation for ln hourly wages on a gender dummy variable, several race dummy variables, a ...
8 views

### p30 accuracy on spss [on hold]

how to calculate 10% or30% accuracy using SPSS? if you have 2 equations to compare it with reference EQUATION i.e to assess the performance and accuracy of both equation in comparison to reference ...
16 views

### Why does Frisch-Waugh produce inconsistent estimates with Weighted Least Squares?

Frisch-Waugh's theorem states that in the setup $Y = X^T \beta$, where $\beta = [\beta_1,\beta_2]^T$, $X = [X_1, X_2]$, $\hat{\beta}_2$ obtained from the multiple regression is the same as that ...
19 views

### Elastic net regularization: mean square error monotonically increases with lambda

This is quite coincidental as my question is nearly identical to this one asked shortly before, but I am also using elastic net regularization with R's glmnet library as a method of variable selection ...
17 views

### A principled method for choosing between t test or non-parametric e.g. Wilcoxon in small samples

Certain hypothesis tests can be approached using Student's t-test, possibly using a Welch correction for unequal variances, or by a non-parametric test such as Wilcoxon paired signed rank test, the ...
12 views

### glmnet- introduce cost function

I'm using glmnet to predict a binary class. I have only 16% of positive cases. Also false negative ( I lose 90 USD) are 9 times more expensive than false positives ...
49 views

### elastic net min deviance when lambda tends to 0

I'm trying to use glmnet packaget to perform elastic net model for binomial regression. I got the following graph: What I see from this is that increasing the lambda never decreases the deviance, so ...
8 views

### build systems for portable analyses

Does anyone have a good tool chain for packaging up, transferring, configuring and running an analysis? Bonus points if an analysis can be reproduced across platforms. There has been a lot of ...
14 views

### > str(“discoveries) returning chr ”discoveries" [on hold]

> str("discoveries") chr "discoveries > str(discoveries) Time-Series [1:100] from 1860 to 1959: 5 3 0 2 0 3 2 3 6 1 ... I'm going through IPSUR and I'm ...
13 views

### How to compare four sets of experimental data and decide if the differences are significant?

For a school science fair project, my daughter randomly divided a population of subjects into a control group and three experimental groups. We recorded the time each subject took to perform a certain ...
16 views

### Getting to predicted values using cv.glmnet

I'm a little confused by the predict function with a cv.glmnet object. I'm running these two lines: ...
16 views

### Weighting p-values

In KEGG pathways (Kyoto Encyclopedia of Genes and Genomes) data set designed as columns and rows. The columns consisted of 50 pathways and the rows are 189 genes. The genes can work in certain ...
7 views

### Partial least squares regression on survey data with multiple scales

I have a survey data set composed of 7 scales, each scale with 7 to 10 items. The theoretical framework I've devised uses 5 of the scales as independent variables and 2 of the scales as dependent ...
7 views

### In an analysis of variance, which of the following is determined by the size of the sample mean differences? [on hold]

In an analysis of variance, which of the following is determined by the size of the sample mean differences? a. SSbetween c. dfbetween b. SSwithin d. dfwithin
40 views

### Use of the term “outcome”

I know that a particular value a variable can have is called an outcome. Sometimes I see that a dependent variable is also called an outcome. Is the latter use a legitimate practice or bad use of the ...
45 views

### What are the consequences of using ANOVA instead of Kruskal-Wallis on non-normally distributed data?

I am doing a high-school statistics assignment and am having trouble finding answer to this question. Anova and Kruskal-Wallis test are very confusing and I am lost trying to find and explanation to ...