# All Questions

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### 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
18 views

1 vote
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 ...
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 ...
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 ...
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
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 ...
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)|...
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
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 vote
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 : ...
10 views

• 1,682
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 ...
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 ...
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 ...
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?
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
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
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 vote
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 ...
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
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 ...
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
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
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
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
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
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
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
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
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
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" (...
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 ...
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
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
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
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 ...
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
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
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