Data Quality and Event Validation in LIGO-Virgo-KAGRA Fourth Joint Observational Campaign

The success of gravitational wave astronomy hinges on precise data quality assessment and the meticulous validation of detected events. This contribution highlights the critical role of these processes within the ongoing O4 observational campaign by the LIGO, Virgo, and KAGRA collaborations. We begin by introducing detector data and the concept of data quality. Next, we examine how common data-quality issues impact the detection of astrophysical signals, affecting both their significance and the reliability of astrophysical parameter estimates. We then describe the statistical methods used to identify and mitigate these issues, followed by an overview of the event validation framework employed in O4 to confirm the astrophysical origins of candidate signals.