When using a multiple baseline design, what is the correct procedure when taking baseline data across all tiers in a single-case research design? Skip the baseline data collection in some tiers and intervene only in the highest-performing tier. Intervene immediately if data is stable across all tiers to see the maximum change. Collect baseline data for a shorter period in the highest-performing tier and intervene right away. If baseline data is stable, intervene; otherwise, baseline logic suggests that the data will remain unchanged if no intervention is introduced. Collect baseline data in all tiers and intervene only if the data shows variability across all tiers