All Questions
194,143
questions
0
votes
0
answers
8
views
Imputed binary response outcome
I am currently working on a group project with COVID data. The response variable is a binary outcome (positive/negative) from swab test; and let's only consider age groups (0-18, 18-60, 60+) for ...
1
vote
0
answers
18
views
Limit distribution of the joint distribution of maximum and minimum of a sequence of random variables
Assume we have a sequence $\mathsf{X}_1,\mathsf{X}_2,\mathsf{X}_3,...$ of iid random variables. Then the Fisher-Tippet-Gnedenko theorem shows that
$$ \mathbb{P}\left(\frac{\max\{\mathsf{X}_1,\mathsf{X}...
2
votes
0
answers
26
views
Variance-stabilizing transformation on a simple linear regression
I am currently working with variance-stabilizer method and readed something about it from my textbook. I want to understand it better so I would like to consider a case where I for instance have a ...
- 131
0
votes
0
answers
7
views
What means to report in longitudinal (repeated data) studies without covariates? Raw meand or model-based (GLS) means? They differ!
I have a study with a few repeated observations per subject, recorded at t0...t3.
I want to assess the change from baseline at each time point and apply the Dunnett adjustment to get the corrected p-...
- 11
0
votes
1
answer
15
views
RFM Customer segmentation - Why Avg monetary value instead of total monetary value?
I am trying to segment our customers based on their purchase data. And I came to know about the RFM technique (Recency, Frequency and Monetary) through these posts here, here etc.
Recency - How ...
- 1,780
0
votes
0
answers
14
views
classifying into 3 groups and measure distribution differences
I'm meeting an issue that I've tried to describe as clearly as possible though I'm sure it would benefit to be reframed in statistics wording, especially the title. Would be grateful to get some ...
- 101
-2
votes
0
answers
32
views
Performing Fisher exact test or prop.test with counts of non-integer numbers?
If most of my count data are have non-integer numbers like (45.5,88.5), can I still use prop.test or fisher test? how that affect the results?
This is how I calculated the counts:
Lets say I have 100 ...
- 191
0
votes
1
answer
30
views
Most suitable regression line
I have loaded the data set Animals2 from the package library (robustbase) and I have ploted three estimated regression lines (least-squares line, the LMS line, and the line of Siegel). I wanted to ...
0
votes
0
answers
13
views
Help with comparing Bayesian linear regression coefficients
Background
I have done a practice problem in Bayesian linear regression and need some help comparing my solution to the official solution to see which solution makes the most sense. The model is
$$
y =...
- 357
1
vote
0
answers
15
views
Evaluate two lossy compression algorithms
I am trying to evaluate several methods to compress some 2D data points.
The algorithm itself is not relevant, but from the output, I can compute the MSE and the number of points (which can be used to ...
- 131
0
votes
0
answers
9
views
Modeling demand distribution with selling constrained by stock
I'm working as a Data Scientist on a project where we are supposed to determine how many pieces of stock a certain retailer should have in each of its physical stores. The stock should be set on the ...
0
votes
0
answers
9
views
anova for model fit return NA
So, i have a continuous outcome and two binary predictors. I want to compare different models between them
...
0
votes
2
answers
27
views
How do you test if the average of a population is the same as the variance of the same population?
What can be a statistical test to find out if a population has the mean equal to its own variance? I.e. Mean(X)=Var(X)?
I am interested in it because Poisson regression makes the assumption that the ...
- 101
0
votes
1
answer
22
views
Assessing the effectiveness of a teaching tool by paired t-test
You have been asked to assess the effectiveness of a new teaching tool. A sample of 25 students from your classes have been tested before and after the provision of the tool, so each student has two ...
- 1
-1
votes
0
answers
13
views
Let random variables X and Y have the following joint density [closed]
Let random variables X and Y have the following joint density:
fX,Y (x, y) = e^−y for 0<x<y; 0 otherwise;
Find marginal density of X and Y, conditional density of X|(Y = y) and show that (Y − X)|...
- 1
0
votes
0
answers
14
views
Kriging is a conditional Gaussian Process?
I'm working with Kriging but its relation with Gaussian processes is still a bit unclear to me, or rather what the difference is. In some literature they mention Kriging is based on Gaussian Processes ...
- 101
0
votes
0
answers
17
views
Non-degenerate discrete random variable X [closed]
Give an example of a non-degenerate discrete random variable X such that X^2 is degenerate. Write down the cumulative distribution function of X with domain R and calculate the variance of X.
I can't ...
- 1
1
vote
0
answers
24
views
Dealing with a warning message from prop.test in R
I did a prop.test for my data and I got this warning message :
...
- 191
0
votes
0
answers
10
views
Validity of equation describing covariance parameter of bivariate lognormal distribution
If $Y∼N(μ,σ^2)$ is normally distributed, then $X=\exp(Y)$ is lognormally distributed. The parameters for a univariate distribution, $\mu$ and $\sigma$ of this lognormal distribution are given by
$\mu{...
3
votes
1
answer
68
views
GAM model warning message: step failure in theta estimation
When running and gam model and this warning message pops up, what does this mean and what is advised? A simple increase in knots (even by 1) seems to remove this warning message.
"Warning message:...
- 49
0
votes
0
answers
12
views
The kernel estimation of conditional density seems to be largely driven by the value of bandwidth. What's wrong with the interpretation?
Suppose I have data $\{Z_{1i},Z_{2i}\}_{i=1}^N$, and I want to estimate the conditional density $f(z1|z2)$ using the nonparametric kernel estimator: $\widehat{f}_{h}(z1|z2)=\frac{\sum_{i=1}^{N}\frac{1}...
- 1,682
0
votes
0
answers
4
views
How to determine the number of pixel from a warped image from a region proposal RCNN
I am learning R-CNN with this slides. On slide 63 one warped image region is specified by 224x224 pixel. Is this just a random value or from where is the value coming from? I cannot see any ...
0
votes
0
answers
7
views
goodness of fit test for model
I did GLMM with negative binomial family. After checking goodness of fit using the equation
"1-pchisq(summary(model4)$deviance,summary(model4)$df.residual)" it gives the value zero. what it ...
- 1
0
votes
1
answer
32
views
Find pdf of X+Y [duplicate]
Let X ∼ Exp(λ) and Y ∼ Exp(μ) be two independent exponential random variables,
where λ, μ > 0.
Find the probability density function of X + Y if λ ̸= μ.
I have successfully find ans if λ = μ, but ...
- 1
0
votes
0
answers
7
views
Why does selective search algorithm for R-CNN extract approximately 2000 region proposals? [closed]
What would happen for example if we would extract instead of 2000 region proposals 1000 or 4000 region proposals?
0
votes
0
answers
12
views
How does the dynamic regression component from TBATS differ from the one in SARIMAX?
Both TBATS and SARIMAX support the modeling of long-term seasonality by using dynamic regression. Dynamic regression in this case involves the use of sin and cos terms to model seasonal components.
In ...
- 2,032
1
vote
1
answer
30
views
Estimate at which point a linear model hits a certain value (including probabilities)
I have a simple 1D set of datapoints with a trend, I want to estimate at which point $X_t$ (i.e., at which point in the future) the model will hit a certain threshold $Y_t$:
I can fit a trendline to ...
- 131
0
votes
0
answers
31
views
Penny's game probablity [duplicate]
Independent flips of a biased coin that lands on heads with probability 0.8 are made. Each of two players, A and B, had chosen one out of the eight triplets: {HHH, HHT, HTH, HTT, THH, THT, TTH, TTT} ...
- 1
1
vote
0
answers
21
views
Seasonal and trend adjustment for irregularly spaced time series
I know of different methods that exist to remove seasonality and trend in the data to make it stationary. However, that exists only for regular time series; that is, a series that follows a fixed ...
- 11
0
votes
0
answers
20
views
Difference between cross validation vs model accuracy measures
I have a time series ARIMA model and I want to validate the accuracy my prediction. But I dont understand the difference of using cross validation vs model accuracy measures such as MAPE, MAE, MSE and ...
- 1
0
votes
0
answers
16
views
is it good to have 100% accuracy on validation?
i'm still new in machine learning. currently i'm creating an anomaly detection for flight data. it is a multivariate time series data that include timestamp, latitude, longitude, velocity and altitude ...
0
votes
0
answers
9
views
Two-Sample Rank Statistics
Assume we got two models, either regression or RF or whatever. I'm trying to observe the relative importance of each feature by using ranks. That is, if we look at a regression model, we have a t-test ...
- 2,351
2
votes
1
answer
85
views
Different Meanings of "Clusters" in Statistics
Typically, I have always come across the term "cluster" within statistics as reference to "clustering" - that is, for example the "K Means Clustering" algorithm. Recently,...
- 5,718
0
votes
0
answers
9
views
Jackknife estimation and testing
I'm using jacknife method to get the uncertainty of my estimation. My estimation restricted to (0,1) and some can be very small. For example, the jackknife estimate for variable A is 0.0000503 and ...
- 11
1
vote
1
answer
24
views
power and sample size estimation
For a one-sided test:
$$H_0: \mu_1 \leq \mu_2 \ H_1: \mu_1 >\mu2$$
$$\alpha=0.025,\beta=0.1$$
How to calculate the sample size needed? Is this information enough to calculate the sample size?
- 451
0
votes
0
answers
14
views
No previous information in a clinical trial
I'm conducting a clinical trial with a treatment group and a placebo group and calculated the sample size based on a previous study. However, I would like to add two more new placebo groups with ...
- 451
4
votes
1
answer
26
views
Finding the MVUE of the center of a circle of unknown location
Is there a known analytic solution for finding the minimum variance unbiased estimator of a disk of an unknown location given that a sample of $n$ points was drawn uniformly and randomly from the disk ...
- 7,082
0
votes
0
answers
9
views
How can I compute rectangular confidence regions for parameters using R?
Simultaneous confidence regions for multivariate parameters (say, a confidence region for multivariate mean, or for regression parameters) usually find an elliptical region when the parameters' ...
- 1,063
0
votes
0
answers
9
views
Principal component analysis (PCA) vs. Partial Least Squares (PLS)
I know the the difference between PLS and PCA estimation procedures.But what is the main output in terms of dimensionality reduction for PCA and PLS?
- 41
1
vote
1
answer
9
views
Measuring value of free users
I was wondering if the following scenario had a word for it (eg. Survival analysis...).
Suppose we have a company that has pro users (pay $10/ month) and free users. I want to calculate the worth of ...
- 1,133
0
votes
0
answers
18
views
GLS vs. OLS with sandwich (or GEE with sandwich?) - repeated data (no covariates!) [duplicate]
Let's assume I have a series of repeated observations at time t0..t3.
I want to test the difference at each time point vs. t0.
When doing a set of independent comparisons "vs. control" (...
- 11
0
votes
0
answers
9
views
Sampling from a Poisson Process
I am trying to simulate a one dimension correlated random walk. In this algorithm, the direction of a particle’s next step is correlated with the direction of it’s previous step. The particle’s step ...
0
votes
0
answers
4
views
Caret: ordinal models with VGAM library
I started to look into the students performance dataset:
https://archive.ics.uci.edu/ml/datasets/Higher+Education+Students+Performance+Evaluation+Dataset
I would like to train two models with caret ...
- 101
1
vote
1
answer
21
views
Can I convert a typical reinforcement learning problem to a supervised learning problem?
I'm not sure if I've understood correctly the whole point of reinforcement learning.
In my point of view, the whole goal of RL is learning a policy that maps states to actions.
Let us suppose that I ...
- 412
0
votes
0
answers
8
views
The expected value of point product of matrices
I have two random binary matrices of the same size m*n. let's call them A, B
I know r_i which is the row sums of A, and c_j which are the column sums of B
what is the expected value of C_ij = A_ij*...
- 551
0
votes
0
answers
10
views
Proper way to report on Confidence Intervals for 2 Proportions means
Disclaimer: Stat noob
Context: I'm trying to figure out the best way to report CI to a non-data/stat/math savy audience.
I'm performing a two proportion z test for an experiment.
Control: 0.3097
...
- 127
0
votes
0
answers
12
views
forward stepwise AIC approach
I am learning about performing stepwise model selection by AIC and I have 2 questions here:
1.Regarding to stepwise AIC, what is contribution (effectiveness) of the number of parameters in the model ...
- 41
0
votes
1
answer
31
views
Correlation of multivariate distributions without "slope"
Wikipedia has this image showing different correlations:
It says:
The correlation reflects the noisiness and direction of a linear relationship (top row), but not the slope of that relationship (...
- 547
0
votes
2
answers
31
views
Why adjustment is needed when calculating Skewness and Kurtosis?
Some packages such as Mathlab, Minitab and SigmaXL caluclate adjustment for skewness and kurtosis.
For example at:
https://octave.org/doc/v4.0.1/Descriptive-Statistics.html
it is suggested that ...
- 101
1
vote
0
answers
14
views
Fitted ARIMA on new time series
Based on the accepted answer from this post: How to use a fitted model parameters for forecasting other time series, it is possible to use a fitted ARIMA model for forecasting another time series. ...
- 81