Fixed vs random effects in Python: what a Hausman test rejection really means

·1 views

A DEV Community tutorial walks through choosing between fixed and random effects panel models using the wage_panel dataset from linearmodels, covering 545 individuals over eight years. The author computes a Hausman statistic by hand, getting chi-squared of 112.118 with 3 degrees of freedom and p near zero, which rejects the random effects assumption. The piece cautions that such a rejection only suggests RE is inappropriate and does not prove fixed effects is correct, since time-varying confounders remain. It also notes that fixed effects cannot estimate coefficients on time-invariant variables and that the classic Hausman test assumes homoskedastic errors, so the Mundlak regression-based approach is suggested for clustered standard errors. The author also mentions an online panel regression tool they are affiliated with.

Read the full story at DEV Community

This is an AI-generated summary. ShortSingh links to the original source for the complete article.

Discussion (0)

Guide Shows How to Pull SEC EDGAR Filings as JSON Without a Custom Scraper

A developer tutorial explains how to retrieve SEC EDGAR filing data in structured JSON form for alerts, compliance checks, and equity research. It notes that EDGAR's endpoints are anonymous and require no API key, but that requests must include a declared User-Agent and stay under 10 requests per second. The article presents steadfetch/sec-edgar-monitor, an Apify Actor that wraps these endpoints and accepts filters by company CIK, form type, date range, or full-text query. Sample code in curl, Node.js, and Python is provided, along with an example filing record showing fields such as accession number, form type, and filing date. Pricing for the Actor is listed at 5.00 USD per 1,000 filings.

0 comments Read more at DEV Community

ProgrammingDEV Community ·

Developer Builds AI Chat Assistant Using Agentic LLMs and Multi-Tool Integration

A developer shared how they built an AI chat assistant that goes beyond a standard chatbot by connecting a large language model to external tools. The project was motivated by the limits of standalone LLMs, which may lack current information and cannot independently access external services. The article explains agentic AI, where the model interprets a request, selects and executes a tool, and then folds the returned results into its reply. Using a weather query as an example, it describes how the assistant would call a weather service rather than rely on the model's training data. The author also links the live demo and the frontend and backend source repositories for readers to explore.

0 comments Read more at DEV Community

ProgrammingDEV Community ·

Kruskal–Wallis Test: A Nonparametric Method for Comparing Three or More Groups

The Kruskal–Wallis test is a nonparametric statistical technique for comparing three or more independent groups. It serves as an alternative when data fails to meet the assumptions required for a one-way ANOVA, and it is applicable in fields such as education, business, psychology, and healthcare. The test checks whether group distributions differ, and it requires independent groups, ranked outcomes, and independence of observations. Its output is an H statistic and a p-value; a p-value below a threshold like 0.05 suggests at least one group differs, but does not identify which ones, so follow-up tests may be necessary.

0 comments Read more at DEV Community

ProgrammingDEV Community ·

Web HIG advises 24px minimum tap targets and 44px for primary touch actions

The Web HIG guidance states that interactive targets must be at least 24 by 24 CSS pixels, matching WCAG 2.2 Level AA, while primary touch actions should ideally measure 44 by 44 pixels. The clickable area, not the visible icon, is what counts, so small icons can be made easier to hit by adding padding. Tightly packed controls such as close buttons, table row actions, and pagination links are common problem areas, since a miss can trigger the wrong action. The guidance notes that people with tremors or limited dexterity, not just touch users, benefit from larger targets. Developers are advised to measure the clickable element's box in browser developer tools and test primary actions by hand on a phone.

0 comments Read more at DEV Community