A clinical trial enrolls 150 hypertensive patients to compare the effect of two antihypertensive drugs on blood pressure reduction. After 12 weeks, mean systolic BP reduction in Drug A group (n=75) is 18 mmHg (SD=6) and in Drug B group (n=75) is 15 mmHg (SD=5). Which test would be most appropriate to determine if this difference in mean BP reduction is statistically significant?