All Questions
211,620
questions
2
votes
2
answers
69
views
How to understand that there are n - 1 degrees of freedom in calculating sample variance? [duplicate]
According to Wiki:
In statistics, the number of degrees of freedom is the number of values in the final calculation of a statistic that are free to vary.[1] Estimates of statistical parameters can be ...
- 51
1
vote
0
answers
19
views
What Are Some Mathematical Functions that Can Represent Surge Pricing for Ride Hailing? [closed]
Consider a ride hailing service, where the fare needs to be dynamically adjusted. I know there are many machine learning driven models possible, but here I am looking for a simpler and sensible ...
- 533
0
votes
0
answers
32
views
Determinant of High Dimensional Correlation Matrix
According to [1] :
The determinant of the correlation matrix will equal 1.0 only if all correlations equal 0, otherwise the determinant will be less than 1 [...] When the measures are uncorrelated, ...
- 73
-2
votes
0
answers
25
views
Doubt on Mann Whitney U test [closed]
I doubt the ranking of 2 values in Mann-Whitney u test? for example, men's and women's social acceptance. If the men's N is small and the female's N is larger, when comes to ranking men have a high ...
1
vote
1
answer
28
views
Can we apply geostatistics on data which is not normally distributed?
If we work on groundwater data, if the data is not normally distributed, can we apply geostatistics on this data without transforming it to normal distribution?
0
votes
0
answers
28
views
Finding the correct formula for a mixed-effects linear regression model
I have the following data:
...
- 215
0
votes
0
answers
21
views
Confidence Intervals Overlaping Although Significant Effects in glmer in R
Below is the output of a glmer:
...
1
vote
1
answer
54
views
When and why is a likelihood ratio preferable to a difference as a test statistic?
We want to know whether two sample sets {x} and {y} were drawn from the same distribution. The null hypothesis $H_0$ is that they are. As statisticians we test the hypothesis by calculating the p-...
- 950
0
votes
0
answers
10
views
How do I report sex differences in meta-analysis when some studies included only report data for one sex?
I am completing a meta-analysis of the sex differences in athlete ECGs. I have included studies that only talk about one sex to broaden the amount of data included. Is there a way to meta-analyse ...
- 1
-1
votes
0
answers
12
views
My total number of respondents are 61, but in frequency it is showing 89. all my frequencies shown are wrong now, please help [closed]
I ran the frequency tests at 1st, it was showing the right numbers (total 61). I had to recode one question, and after recoding it, the frequency for all the questions shows a total of 89, however, it ...
0
votes
0
answers
16
views
What linear formula is this model fitting? [closed]
The rstatix R package has a wrapper around the aov called anova_test. It allows to pass ...
- 215
1
vote
1
answer
20
views
Time series model without ARMA component and with exogenous variables
I am trying to know what is the most simple model for time series data, with exogenous variables. What is the most simple framework I can use ? Is it possible to build a model more simple than ARIMAX, ...
0
votes
1
answer
37
views
Does the matrix notation for OLS loss function assume that indexing a row from $X$ return a column or row vecotr?
I'm confused about the matrix notation of the loss function in ordinary least squares regression. In matrix form, the expression for a linear model is:
$$\hat{y} = Xw$$
Where
$\hat{y} \rightarrow$ ...
1
vote
0
answers
8
views
Custom contrasts in piecewise mixed effects models
I have longitudinal data from a two-group RCT in which the primary outcome was assessed at baseline, each week during the intervention, post-test and 5-month follow-up (6 times total). I am modeling ...
- 11
2
votes
1
answer
25
views
Derivation of acceptance probability from Linero, Yang (2018)
I am wondering how this paper Bayesian Regression Tree Ensembles that Adapt to
Smoothness and Sparsity by Linero & Yang (2018) derived the acceptance probability for $\sigma$.
The authors give $\...
5
votes
3
answers
143
views
How to interpret the population parameters of a Bayesian Hierarchical model?
This is almost certainly a fatal misunderstanding of mine / knowledge gap but I am confused as to how to interpret the population parameters of a Bayesian Hierarchical model.
This is incredibly ...
- 758
0
votes
0
answers
7
views
Mutual information between a vector of values and a statistic computed on the vector
I understand that the mutual information between two vectors X, Y from two distributions gives a measure of uncertainty of X knowing information about Y. But is it possible to measure mutual ...
- 11
0
votes
0
answers
14
views
Interactions in regression and choosing appropriate model?
I’m running the following regression model, where MR is a continuous predictor and grade, gender, and race are all categorical.
DV~MR + grade + gender + race
I’m also interested in how the 3 ...
- 11
0
votes
0
answers
3
views
Why detections count is not equal to unique truth count in YOLOv4 test result report?
I trained model using YOLOv4 on GPU, CUDNN and openCV (python) with AlexeyAB\Darknet with multi-label on windows environment. These labels are 25 classes (from 0 to 24). Then I test the model and I ...
- 1
0
votes
0
answers
16
views
Modelling 3-level MLM of longitudinal data in R
I have two questions regarding modeling a 3-level multilevel model in R.
I have a dataset of different variables that were assessed 4x as part of a longitudinal study. At each of the four assessments ...
- 1
3
votes
0
answers
55
views
On an infinite linear combination of chi-squared random variables
Question
Let $Z_i\sim\chi_{(1)}^2$ be i.i.d. chi-squared random variables with 1 degree of freedom. We define:
$$
W_{\infty} = \sum_{k = 1}^{\infty} \frac{Z_k}{2^{k}}
$$
I have interest in computing ...
- 131
0
votes
0
answers
51
views
Why does weights argument in glm change the outcome of lsd?
I have dataframe df.
...
0
votes
0
answers
12
views
Drawing Circular histogram in R [closed]
I want to visualize my results as in this diagram. I have p-values, log2 FCs and metabolites. how to create this in R. please help me. I am new to this.
1
vote
0
answers
22
views
Finding the smallest possible sample size of a 2x7 contingency table, given row-wise proportions and relation between row marginal counts
NB: this is not about power analysis.
Consider the following table, which has the following row-wise proportions:
cat_1
cat_2
cat_3
cat_4
cat_5
cat_6
cat_7
A
0.3222449
0.302041
0.208163
0.089796
0....
- 3,123
0
votes
0
answers
11
views
Adapting the Viterbi Algorithm [closed]
I'm currently doing an NLP course , and am going through some past papers but am stuck on this question (in the context of tagging , specifically for named entities , e.g. people organisations etc . ) ...
- 1
0
votes
0
answers
8
views
Tests for comparing ratio data from independent samples
The data are from an international study comparing participants' perceptions of how much more corporate CEOs make compared to unskilled workers (median ratios are used because mean ratios did not pass ...
- 1
5
votes
1
answer
243
views
Why can a model's SHAP values change on a new dataset?
Background
I'm validating a model and as part of the process I've been calculating SHAP values for different validation datasets.
I've calculated SHAP values for every sample in each dataset taken ...
- 441
2
votes
0
answers
22
views
Why are residuals correlated with prediction when using linear mixed model with low number of observations per group?
I have a database composed of n = 1000 observations of a variable to explain (y), an explanatory variable (x). The observations are grouped according to a variable "group", and I have only ...
- 21
0
votes
0
answers
17
views
Difference in Difference Regression (Showing a change in independent variable coefficient for treat-post group)
I want to measure the the change in the relationship between one of my independent variables (gold price) and my dependent (conflict deaths) for my treatment post group. Any help would be greatly ...
- 1
3
votes
1
answer
81
views
Unbiased estimator of $\sigma^4$
In the post [here], the user asked the question
$\{X_i\}_1^n$ is random sample from $N(\mu, \sigma^2)$ with unknown parameters. Find an unbiased estimator of $\sigma^4$.
The solution uses a property ...
- 1,579
0
votes
0
answers
5
views
link log and identity in GLMER
Say that we have a GLM model with the following formula:
outcome = b1x1 + b2x2 + b0
and outcome is cost, x1, x2 are independent variables
Fitted using log link with gaussian distribution, so log ...
0
votes
1
answer
29
views
Survival Analysis: Treatment not assigned at the beginning of the observation period
I am new to the field of survival analysis and looking for recommendations on how to deal with the following scenario:
I have data on patients suffering from a certain disease. Some patients receive ...
- 13
0
votes
0
answers
25
views
Data mining for categorical variables that correspond to modes of a continuous variable
Is there a good method or test to find categorical variables associated with modes of a continuous variable?
Take the velocity of a car as an example. You would expect there to be at least two modes ...
- 88
0
votes
0
answers
5
views
How does the training set size affect the uncertainty (variance) of performance estimation?
I am reading this paper which discusses the factors that affect the uncertainty (variance) in the performance estimation of a learner.
The authors say (p. 2, "The monotonicity of the learning ...
- 452
0
votes
0
answers
16
views
which statistical test should be used for testing the significance of the mean differences in time series data?
I was looking to investigate if the monthly total return of US Treasury bond index depends on the magnitude of the US inflation readings.
So i downloaded the US CPI YOY monthly data for the last 50 ...
- 547
1
vote
1
answer
13
views
AB Testing with and without counterfactuals
My boss wants us to run a simple experiment where we manipulate the search results on our website. He is insisting that we must have counterfactuals for the results to be valid. The way I see ...
- 169
0
votes
0
answers
21
views
GAM of complex time-series: how to solve strong temporal autocorrelation?
I have a time-series of data from quasi-continuous sampling over multiple years and different sites. I'm interested in the diel scale at the various sites.
I a priori know that:
we have overall inter-...
- 241
0
votes
1
answer
25
views
GLM vs Kruskal-Wallis/ANOVA?
I am trying to analyse some data in R that has one continuous dependent variable (x) and two categorical variables (sex: M/F, surface: D/V). My main goal is to understand if sex and surface affect 'x'....
- 11
0
votes
0
answers
9
views
What are the main differences between a traditional receiver-operating curve and a Lorenz curve?
I am analyzing a dataset of cardiac echocardiographic exams, aiming to compare the diagnostic accuracy of a novel test in comparison to a standard one.
I have recognized that using Stata I can ...
- 2,504
1
vote
0
answers
15
views
Statistical significance of "bump" in DFT magnitude
I am simulating data according a statistical model and then calculating the magnitude of the DFT of the empirical histogram (full MATLAB code below). If the parameter ...
0
votes
1
answer
52
views
Consider $X_1, \cdots, X_n$ which are iid and have common pdf $f(x | \theta) = e^{-x+\theta}$ $(x > \theta)$
Consider $X_1, \cdots, X_n$ which are iid and have common pdf $f(x | \theta) = e^{-x+\theta}$ $(x > \theta)$. Why is $$\frac{f(x|\theta)}{f(y|\theta)} = \exp \left\{{\sum_{i=1}^{n} (y_i-x_i)}\right\...
0
votes
0
answers
7
views
Random forest for feature selection over large inhomogeneous data set
I have a very large dataset (500,000 examples, 3000 features with a lot of missing values). I want to run a random forest algorithm for feature selection with sklearn. Unfortunately, I cannot load the ...
2
votes
2
answers
46
views
Which type of t-test is best to use for my data
I'm looking for some guidance on which type of t-test is most suitable to use for my data.
I want to compare the means of the variable 'Rate' between two groups in my data. I have 6 years of data and ...
- 21
0
votes
0
answers
29
views
GLM or GLMM design for different tasks
I am conducting a study involving 70 participants diagnosed with Mild Cognitive Impairment (MCI) and 75 without MCI. All participants were engaged in taxonomic semantic, thematic semantic, and ...
0
votes
0
answers
10
views
Power-law fitting with x-y relationship [closed]
I would like to fit a power-law distribution to data taking into account the x-y-relationship. I tried plfit & powerlaw package for python. But the problem with them is that if I shuffle the y-...
- 1
2
votes
0
answers
59
views
Random correlation matrices
Suppose that we simulate random correlation matrices by assigning iid $U(-1,1)$ random variables to all off-diagonal entries and accept matrices $\boldsymbol\Sigma$ that are positive definite. The ...
- 10.5k
2
votes
1
answer
24
views
How can I tell if a clutser-randomised crossover trial has made a unit of analysis error?
I am studying the following paper:
https://jamanetwork.com/journals/jama/fullarticle/2698491
This is a cluster randomised control trial with crossover. I want to ensure they have not made a unit of ...
- 343
0
votes
0
answers
18
views
Questionable results using powerCurve on nbinom2 glmer [closed]
I have a problem with a power analysis using powerCurve. The data show a drastic decrease over time, but powerCurve suggests that I would need data from over 100 sites, to be able to show this. I get ...
- 1
4
votes
1
answer
175
views
Does it make sense to fit linear regression on single-case studies?
Just on principle, do you think it would make sense to make linear regression models for each individual in a study and treat replicates as data points? I don't mean reporting p-values or anything ...
0
votes
1
answer
35
views
How to perform a 2 sample Kolmogorov-Smirnov test controlling for a type II error instead of type 1
I have four completely different sets of two samples and want to check for each set if both samples come from the same distribution, so four Kolmogorov-Smirnov tests total. If it's going to be ...
- 11