Final answer:
The observation method used to compare a child's development to others of the same age is structured observation, which allows for specific behaviors to be elicited and compared in a controlled manner.
Step-by-step explanation:
The observation method used to compare a child's development to other children of the same age would typically be structured observation. This method involves observing children as they engage in specific tasks that are designed to elicit certain behaviors. This type of observation allows researchers to compare the responses and behaviors of different children in the same age group under controlled conditions. An example of structured observation is the Strange Situation by Mary Ainsworth, which assesses attachment styles between infants and their caregivers. Through a series of introduced phases, such as a stranger's entry and the caregiver leaving and returning, the child's reactions can be closely monitored and compared.