Sampling design in observation includes choosing the target population (people, acts or events, behaviors, etc.) and the appropriate approach (probability vs. nonprobability). Two sampling methods are unique to observation: event and time sampling. Event sampling measures all factors involved with a single specified event, while time sampling chooses a time interval and records desired variables within that time frame. There are three types of time sampling (time point, continuous time, and time interval). In data collection design, we must address seven different factors: content type (facts or acts, inferences of those acts, or both), type of observation (nonbehavioral or behavioral), the environment (field or laboratory), data collection protocol (simple observation or systematic observation), observer presence (direct or indirect observation), observation concealment (full, partial, or none), and observer involvement (participant observation or none). The measurement instrument for observation research is the observation checklist.