1
vote
1answer
19 views

how to random sample proportional to probabilities

I have a ten-sided die, where I know the probabilities of rolling some, but not all of the values on the die: ...
0
votes
0answers
16 views

K-Nearest Neighbour Classifier accuracy [migrated]

I followed an example of the MATLAB KNN classifier with 10 fold cross validation, I am lost at the stage of computing the model's performance, Please kindly look at my code below and advice on how i ...
1
vote
0answers
15 views

Proof about an Inhomogeneous Poisson Process

We know that an inhomogeneous Poisson process is a process with a rate function $\lambda(t)$. That is, for any time interval $[t, t+\Delta t]$, $P\left \{ k \;\text{events in}\; [t, t+\Delta t] \right ...
1
vote
1answer
14 views

Interpretation of absurdly large (but probably correct) Bayes Factors?

I estimated a Bayes factor to compare a hypothetical model against a null-model (which obviously by visual comparison of the posterior predictive with the data) fails to capture a certain aspect in ...
3
votes
0answers
26 views

Show that the sample covariance converges in probability to the $Cov(X,Y)$

Suppose we are given $[(Y_i,X_i)]^{n}_{i=1}$ which is a random sample from the joint distribution of $(Y,X). Show that the sample covariance converges in probability to the $Cov(X,Y)$ My thought ...
1
vote
0answers
21 views

Is representativeness a necessary condition for generalisability?

If a large sample of volunteers were not representative of a specific population, would it necessarily mean that any conclusion of a study performed with sound methodology on this sample could not be ...
0
votes
1answer
17 views

IBM SPSS QUESTION: Measure the perception of the respondents

My problem to solve with IBM SPSS is: I have got answers to a question about X topic that contains 15 options of multiple response and I want to characterize the perception of the correspondents ...
1
vote
0answers
9 views

Repeated measures ANOVA with custom standard errors

I want to see if there's a difference in size of some cells after several measurements, compared to a baseline (0.5, 1, 3, 6 hours versus 0 hours). I have 3 samples. Each measurement is actually a ...
1
vote
0answers
26 views

how to determine if two dice are fair using pymc and roll data

My scenario is that I have two six-sided dice (D1 and D2), either of which may be fair or loaded (biased). I have samples of combined roll data (i.e. D1 + D2). I would like to view the posterior ...
0
votes
0answers
5 views

Partial least squares for expression datasets

I'm quite new to the applications of partial least squares regression analysis, and was hoping I could get an overview of how this analysis can be applied to the datasets I have. I have two datasets: ...
1
vote
1answer
31 views

What is the distribution family where one side is with light tail but the other side with heavy tail?

For example the distribution of weights of human. There are not many adults under 40 kg, but a lot more people heavier than 100 kg, although the average of an adult's weight is, let's say, 70 kg. ...
1
vote
0answers
4 views

is there no need for a washout period when using Balaam Design

Balaam design is a crossover design for comparison of regimen A with regimen B in which subjects are randomly allocated to one of four sequences: AA, AB, BA or BB. Sequence AA means that the ...
2
votes
1answer
33 views

How is the Akaike Information Criteron applied for model with large number of predictors?

I am reading a paper (details not very relevant) which assumes that the market cost $C$ of a trade is related to $N$ predictors $X_1,\dots,X_N$ (page 25) through a linear relationship $$C = \beta_0 + ...
1
vote
0answers
19 views

Observed versus hidden variables for Bayesian network in this particular context

I am a novice in Bayesian networks. I have a problem which is best described (at least I think so) in the following story. One wants to predict earthquakes. Let's say it has 5 variables, the last one ...
13
votes
4answers
1k views

Is p-value essentially useless and dangerous to use?

First are some background information. This article "The Odds, Continually Updated" from NY Times happened to catch my attention. To be short, it states that [Bayesian statistics] is proving ...
1
vote
0answers
9 views

Can I use a Spearman Rank-Order Correlation test to check the impact of potential confounders in my data?

I have a relatively basic statistics knowledge, so I apologise in advance if this question doesn't fully make sense or if I'm totally off-base with how I'm trying to analyse it. I've got a project ...
0
votes
0answers
19 views

Showing that moment estimates are asymptotically bi-variate normal

Let $X_1,\dots,X_n$ be iid $\Gamma(p,1/\lambda)$ with density $g_\theta (x) = \frac{1}{\Gamma(p)} \lambda^p x^{p-1} e^{-\lambda x}$, $x>0$, $\theta = (p,\lambda)$, $p > 0$, $\lambda > 0$. ...
0
votes
1answer
38 views

pruning Neural Network

Since a feedforward NN with a logistic function as activation function is not linear, does it make sense to reduce variables first with principal components or discriminant analysis? Because ...
0
votes
0answers
21 views

How to calculate PRESS and $R^2_{predicted}$ in Stata automatically [migrated]

So I have two models and I want to calculate these statistics. Is there any package to calculate them in Stata? PRESS statistic (wiki) And, if I am not mistaken. $$ R^2_{predicted} = 1 - ...
6
votes
2answers
204 views

pdf of a product of two independent Uniform random variables

Let $X$ ~ $U(0,2)$ and $Y$ ~ $U(-10,10)$ be two independent random variables with the given distributions. What is the distribution of $V=XY$? I have tried convolution, knowing that $$h(v) = ...
2
votes
0answers
19 views

How to estimate parameters of a nonlinear function with log-normal error?

Consider you have some nonlinear function \begin{align} y_i&=\epsilon_i f(\beta,x_i) \end{align} where $\epsilon_i$ is log-normally distributed with mean 1, and \begin{equation} ...
0
votes
0answers
7 views

Input normalization effect on Polynomial regression

Here there is a good explanation proving that column normalization does not affect linear regression. But I need to know if this is the same in polynomial regression as well. Thanks in advance,
0
votes
1answer
19 views

indicator variable - dirac delta or step function

I am trying to solve the following equation, \begin{equation} = \int_{-\infty}^{\infty} \frac{1}{\sqrt{ (2\pi)^{k_{Y}} | \Sigma |}} \cdot \mathrm{exp} \{ -\frac{1}{2} (Y - Xm)^{T} \Sigma^{-1} (Y ...
0
votes
1answer
8 views

Analysis of microbial community data collected from iPad swabs

We have taken a number of swabs (~200) from iPads used in our clinic, and after the first half we've introduced an intervention to disinfect all iPads after every use (in addition to the standard ...
0
votes
0answers
7 views

biased random guess classification

I try to get used to some classification methods in R (kNN, Decision Trees, SVM) and I am just wondering: Is there a way to do a biased random guess classification to see the real performance of the ...
3
votes
1answer
42 views

Can I do panel regression if all my covariates are time-invariant?

We have a data set where our outcome of interest varies over 10 years, but the explanatory variable of interest and all of the potential confounders are time-invariant. I am quite certain that a panel ...
4
votes
1answer
40 views

Are prediction and distribution-fitting ever not the same thing?

Intuitively, it seems to me that, if one is able to make accurate predictions about a variable, then one has also (perhaps implicitly) produced a good estimate of its marginal or conditional ...
0
votes
0answers
4 views

How was the explicit closed form for this implicit function derived? [migrated]

The problem comes from reading this [0] paper but I think I can express it in a self contained question. Consider the implicit function $H(z)$ defined by the relation: ...
-1
votes
0answers
34 views

When to use K mean clustering and hierarchical clustering algorithm? [on hold]

Can you please tell me when to use the K-mean clustering and hierarchical clustering algorithm and what is the different between them... Regards, Rahul
2
votes
1answer
80 views

Is a gamma distribution bounded between 0 and 1 the same as a beta distribution? [on hold]

After making the assumption that monetary losses could be well represented by a gamma distribution (Boland, 2007), mostly negatively skewed, and being interested in loss ratios (ie. lost value / total ...
0
votes
0answers
4 views

Adding a trend line to a scatterplot using R [migrated]

I have a data set with number of people at a certain age (ranging from 0-105+), recorded in the period 1846-2014, and I am making a scatterplot of the summed amount of people by year; there's one data ...
3
votes
3answers
71 views

Explanation on a Minsky's critique on statistical learning related to XOR

I was listening to the first session of society of Minds by Minsky (2011) and he mentions at some point around minute 48 the following: "...lots of statistical learning tools is good for lots of ...
0
votes
0answers
25 views

Statistical Significance of a Sample [on hold]

Background: I do not know anything about the population except the population size (N). All I have is a sample. Question: How to I test if this sample is statistically significant (e.g. 95% ...
2
votes
2answers
37 views

Mean Preserving PDF Spreading

I have a histogram representing the PDF of an unknown discrete RV. The histogram is asymmetrical. To be clear, all I have is the histogram. Is there a known way to increase/decrease the variance of ...
1
vote
0answers
15 views

help with sample size calculation

hi im conducting a study on a certain ratio in a blood exam (lets call it X) . I aim to say that there is a certain sensitivity (let say>80%) for people to be sick if X>10. (my actual intent is to ...
0
votes
0answers
7 views

relation between accuracy and tpr/tnr

If a test is 99% accurate, does that always mean that TPR is 99% and TNR is 99%? Im trying to understand the baserate fallacy
0
votes
0answers
5 views

confidence interval for I square [on hold]

in my metanalysis I got a negative I square value (Q=2.040; df=4). I will report it as zero. Do I need to report confidence interval for I square? Is it O.K to use fixed effect model for above ...
0
votes
0answers
10 views
1
vote
1answer
32 views

On Negative AIC Values

My question is related to the thread Negative values for AIC in General Mixed Model. I often get negative AIC values from the software I use. I notice it most when I'm doing time series. But here ...
1
vote
2answers
40 views

How can I model a binary outcomes in time series using logistic regression?

My data has a binary outcome (attack or not attack), day (20 day in repeated measured design) and some covariates (nestling’s movement). The objectives of my experiment are testing the effect of time ...
0
votes
2answers
18 views

Inferring on an unknown number of function approximation

I want to ask whether a procedure to do the following job exists (or whether it makes sense for it to exist). First, assume we have $k$ functions $f_1,...f_k$ that have the same domain and range. ...
0
votes
0answers
14 views

proportion and stats [on hold]

A study of accident locations on a level, 6-mile bike path shows that accidents occur uniformly along the length of the path. There is a stream alongside the bike path between the 3.2 mile-mark and ...
2
votes
1answer
35 views

Multiple regression with correlated variables

I am trying to do multiple regression analysis of a continuous health variable (yval) keeping age, gender, height (cm), weight (kg) and waist (cm) as predictor variables for a database of about 7000 ...
0
votes
0answers
11 views

test of correlation among binary variables prior to running logistic regression analysis

I am running a logistic regression analysis with binary variables on SPSS: dependent variable: preterm birth (Y/N) independent variables: hypertension (Y/N), diabetes (Y/N), C section (Y/N), ...
0
votes
0answers
6 views

troubleshooting R BayesFactor package - error in regressionBF [on hold]

I want to use regressionBF to run all subsets regression. Here is my code: fitness.bf = regressionBF(VO2 ~ ., data=fitnessdata) and here is the error it spits out when I try and run the code: Error ...
0
votes
0answers
6 views

Sample size calculation to compare variables from multiple groups [on hold]

I'm going to conduct an in vitro model experiment to compare a continuous variable between 5 groups. I would like first to calculate the sample size needed for every group. I have used online ...
1
vote
3answers
83 views

Covariance greater than Variance?

It is straightforward to verify that for two random variables $X$ and $Y$ with variances $\sigma^2_X \neq \sigma^2_Y$, we have that $$\Big|{\rm Cov}(X, Y)\Big| \leq \max\{\sigma^2_X,\, \sigma^2_Y\}$$ ...
5
votes
1answer
45 views

can someone fix this cognitive dissonance I have about marginals?

Consider two Bayesian updates, where there are two observations. One updates with respect to $x_1$, and then uses the posterior of that as a prior to update with respect to $x_2$. In both cases, $x_1$ ...
4
votes
2answers
50 views

If $E[Y|X]=a$ for some constant $a\neq 0$, then does $cov(X,Y)=0$?

I'm currently working on the following problem: Q: If $E[Y|X]=a$ for some constant $a\neq 0$, then does $cov(X,Y)=0$? Now I am quite lost as to how to do this problem as the question does not ...
1
vote
0answers
10 views

prediction with string similarity

Assume we have an input of an email and we want to predict if it is spam or not spam. Without being a statistician, i would think one of the predictors takes the subject of the input email and ...

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