A clinical researcher in Mumbai compared the mean systolic blood pressure (SBP) between two independent groups of hypertensive patients: those on antihypertensive therapy for 6 months (Group A, n=45) and those on therapy for 12 months (Group B, n=50). Both groups had approximately normally distributed SBP values with similar variances. Which test is most commonly used to determine if there is a statistically significant difference in mean SBP between the two groups?