This question evaluates a data scientist's competency in defining and measuring push-notification quality by selecting relevant engagement, retention, and opt-out/uninstall metrics, setting thresholds, and designing randomized experiments to validate a notification-selection algorithm.

A consumer mobile app sends push notifications to drive user engagement. You need to evaluate the quality of these notifications, define what constitutes “high-quality,” and design a rigorous experiment to validate a new notification-selection algorithm at launch.
Assumptions (minimal):
Hints: Consider engagement, retention, opt-outs, control vs. treatment setup, and sample size.
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