¿Por qué se considera una buena práctica excluir los valores NULL user_id de las consultas de alcance y frecuencia?

Excluding NULL userid values from reach and frequency queries is crucial because these metrics rely on identifying unique users. A NULL userid indicates that the system cannot identify a specific user, making it impossible to accurately count unique individuals (reach) or how many times they were exposed (frequency). Including these records would artificially inflate the total number of impressions without contributing to a meaningful understanding of user engagement, thereby skewing the results and leading to inaccurate campaign performance assessments. The other options are incorrect because NULL userid records are not automatically removed in prior processing stages, nor are they inherently considered invalid traffic in all server-side post-impression models; their exclusion is specifically about the integrity of reach and frequency calculations.