# All Questions

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### How was the skewness formula made/derived?

The skewness formula that shows up when I Google it is: I know what each of these values are individually, but I’m having a hard time seeing intuitively why this specific formula give a value for ...
• 13
3 views

### Hypothesis testing for increase in sales

A company is planning to setup the option for self checkout (SCO) in all of its stores. As a trial, they are looking to estimate the benefits of SCO in terms of increase in transaction volume by ...
1 vote
6 views

### Relationship between Survival Distributions and Log Linear Regression in Accelerated Failure Time models

The accelerated failure time model (AFT) can be expressed as: $S_{1}(t) = S_{0}(\frac{t}{\gamma})$ where $S_{0}$ is a specified baseline survival distribution and $\frac{1}{\gamma}$ is the accelerant/...
• 11
15 views

### Finding the chi-squared distribution of a squared difference of two independent normal variables

Given two independent random variables $X\sim N(0, \sigma), Y\sim N(0, \sigma)$, what is the distribution of a variable $Q = (X-Y)^2/4$ ? What would be the expected value and variance of $Q$?
6 views

### Are these two events independent (Comey and Mccabe tax returns)? How would we tell?

The NYT reports: The former F.B.I. director and his deputy, both of whom former President Donald J. Trump wanted prosecuted, were selected for a rare audit program that the tax agency says is random. ...
5 views

### I have two different data sets, uneven in terms of number of species. I haven't found good recent examples of publications with 2 phylogenies

Thanks for reading me. I have two different data sets, uneven in terms of number of species. The first one has 20 plant DNA sequences, and the second set is a morphological matrix with 95 species (...
5 views

### If partial regression coefficient is zero, then $Y$ is independent of $X_i$ conditional on all other regression variables

In a textbook Causal Inference in Statistics - A Primer (p. 81), it says Given the regression equation $$y=r_{0}+r_{1} x_{1}+r_{2}x_{2}+\cdots+r_{n} x_{n}+\epsilon$$ if $r_{i}=0$, then $Y$ is ...
13 views

### p-values of Spearman correlation test: Different reporting between R and Python [duplicate]

I am using scipy's spearmanr and R's cor.test with method=spearman to estimate the p-value of the spearman correlation test when applied to some data. When I run the python code I get when I do it R, ...
8 views

### Correlation of groups in simulating data

I am simulating time series data. Each simulation consists of a group of time series with nodes at lets say 3 levels. To get the data to adhere to the structure I only generate the terminal units (...
5 views

### How to sample for compliance when a portion of the population is already known to be non-compliant?

Say I wanted a representative sample to estimate the portion of a population that is compliant on "doing their taxes correctly". Normally, I'd do a random sample of that population to make ...
• 303
9 views

### Probability that two specific people are selected for IRS audit within 4 year period

A recent NYTimes article states that The minuscule chances of the two highest-ranking F.B.I. officials — who made some of the most politically consequential law enforcement decisions in a generation —...
• 3,778
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### How to compare observed versus expected ratio data between two independent, unpaired groups with different sample sizes?

so I'm comparing the expected fitness of double mutant animals (based on independent, additive effects of each corresponding single mutant) to the observed fitness of the double mutant. The data is ...
23 views

### What is wrong with treating everything as a hyperparameter?

I've seen a number of questions like this asking whether certain parameters can be treated as a hyperparameter. Why can't we just treat everything as a hyperparameter? I understand that this is an ...
• 141
7 views

### Sample size estimation for difference-indifference design with continuous outcome

I have spent some time looking for a package in R to estimate the required sample size for a difference-in-difference design with continuous outcome. However, I could not find any package. Is there a ...
21 views

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1 vote