Follow a complete testing sequence

State H0 and H1, α, assumptions, statistic and null distribution. Compute SE, then the signed statistic. Use the correct tail or p-value, make a decision and interpret in context. Two-sided t testing rejects when |t| exceeds its upper 1-α/2 quantile. Left-tailed testing rejects for sufficiently negative t. Do not turn a signed left-tailed statistic positive before applying a one-sided rule.