The manager should stop production to set the machine to fill the bags more.
Since the sample mean (2.38 lbs) is less than the expected mean (2.5 lbs), it suggests that the bags are being underfilled by the filling machine. The calculated t-value of -1.247 is less than the critical t-value of -1.703 (with 26 degrees of freedom and a significance level of 0.05). This means that we fail to reject the null hypothesis that the bags are being filled at the correct weight. However, since the sample mean is significantly lower than the expected mean, the manager should take action and adjust the filling machine to fill the bags more to meet the expected weight.