You suspect that high school students who have been attending school in-person during the pandemic will have higher test scores on average than students who attended school online. You take samples of 20 students from each group; you find a mean of 73.7 for the sample of in-person students, and 68.9 for the online students. Assume that you know the population standard deviation for each group (12 for both populations). Use 'in-person' as population 1 and 'online' as population 2.

A)What is the z or t score to be used.

B)What is the margin of error ?