When does sampling occur in Analytics 360 reports?

Sampling in Google Analytics 360 primarily occurs when an ad-hoc query exceeds the sampling threshold for sessions. For 360 accounts, this threshold is significantly higher (100 million sessions) compared to standard accounts (500,000 sessions), but it still exists. When a custom report or ad-hoc query requests data that surpasses this limit, Analytics will sample the data to generate the report faster. A high cardinality dimension does not directly trigger sampling; rather, it can make sampling more likely if the query involves many unique values and a large dataset. Standard reports generally do not sample, regardless of the data range, as they are pre-processed. While there is a sampling threshold for sessions, it specifically applies to ad-hoc queries, not standard reports.