> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fincept.in/llms.txt
> Use this file to discover all available pages before exploring further.

# Instrumental variables

> Instrumental-variables regression for endogenous regressors: two-stage least squares, LIML and k-class (Fuller), GMM and continuously updated GMM with robust, HAC or clustered weighting, first-stage strength, over-identification (Sargan, Basmann, J) and endogeneity (Durbin, Wu-Hausman, C) tests, and side-by-side comparison of estimators.

Toolset `panel_iv`: 2 tools.

| Tool | What it does | Notes |
| - | - | - |
| `panel_iv_regression` | Linear instrumental-variables regression of a dependent column on exogenous and endogenous regressors with excluded instruments. | |
| `panel_iv_compare` | Fits several instrumental-variables estimators (and OLS, which treats the endogenous regressors as exogenous) on the same specification and lays them side by side: coefficients, standard errors, t statistics and p-values per estimator, with observations, R², adjusted R² and F per estimator. | |

Inputs, limits and outputs are described in [Fincept Panel](/guides/fincept-panel). Full schemas: `fincept_describe_tool`.


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