Describe a process you could use to get a simple random sample of size 20 from a class of size 40.
Assign each student a number 1, 2, . . . , 40 and use a computer or a random-number table to select 20 students.
Assign each student to a pair 1, 2, . . . , 20 and use a computer or a random-number table to select 10 pairs.
Assign each student a number 1, 2, . . . , 20 and use a computer or a random-number table to select 10 students.
Assign each student a group 1, 2, 3, 4 and use a computer or a random-number table to select 2 groups.

Question

Describe a process you could use to get a simple random sample of size 20 from a class of size 40.
Assign each student a number 1, 2, . . . , 40 and use a computer or a random-number table to select 20 students.
Assign each student to a pair 1, 2, . . . , 20 and use a computer or a random-number table to select 10 pairs.    
Assign each student a number 1, 2, . . . , 20 and use a computer or a random-number table to select 10 students.
Assign each student a group 1, 2, 3, 4 and use a computer or a random-number table to select 2 groups.

anonymous · Answer

i am not sure but i believe that choosing first option seems more appropriate because the probability of each student to be chosen is 1/40 compare to other option this the largest one and will give u a good random sample :)

mathmale · Answer

The first option is also the simplest.  Every student has an = chance of being chosen.    In the other options, "pairs" or "groups" are chosen; this is NOT necessary or appropriate for "simple random samples."     

I agree with your  "the probability of each student to be chosen is 1/40"

I don't really grasp or approve of your "compare to other option this the largest one and will give u a good random sample"

Best to review the meaning of "simple random sample"