Dear Hazrienne,
Our rule of thumb of buying into a stock is when the four-quadrants are all fulfilled.
Since the stock is already ended in a portfolio, I would make an assumption that the quality of the target stock is rock-solid, comparable to those in existing portfolio and yet if the share price dropped by 20%, I may consider averaging down is better alternative if my portfolio is already well-diversified across twenty stocks distributed across different industries. If it is less than ten stocks, I will simply add on new position (assuming the stock is as attractive as those in my portfolio) to manage risk from portfolio level.
