If you are specifically testing whether the program increases quality of life (but are not interested in whether it could decrease it), a one-tailed test would be appropriate. However, if you are open to testing whether the program could either increase or decrease the quality of life, then a two-tailed test would be more suitable. In most cases, a one-tailed test might be used here, as the primary interest is likely to be in improving quality rather than considering a negative impact