Use 'ineffective' when an action doesn't lead to the desired result, regardless of effort made. Despite studying hard, his methods were ineffective for the final exam.
Pro Tip 2/3
Negative Implication
'Ineffective' often implies disappointment or failure to meet expectations. Her speech was ineffective, leaving the audience unimpressed.
Pro Tip 3/3
Alternative Solutions
Use 'ineffective' to suggest that a different method may be needed. The advertising campaign was ineffective, so we need a new approach.