2.1 This is not a simple random sample. Not every possible group of four students can be selected. For example, four students sitting in the same row can never be selected.

2.2 Step 1: Label. For the 20 teaching assistants (TAs), we use labels

01, 02, 03, . . . , 18, 19, 20

Specifically, the list of TAs with labels attached is

(01) Alexander(11) Park

(02) Bean(12) Race

(03) Book(13) Rodgers

(04) Burch(14) Scarborough

(05) Gogireddy(15) Siddiqi

(06) Kunkel(16) Smith

(07) Mann(17) Tang

(08) Matthews(18) Twohy

(09) Naqvi(19) Wilson

(10) Ozanne(20) Zhang

Step 2: Software or table. We used the Research Randomizer and requested that it generate one set of numbers with three numbers per set. We specified the number range as 1 to 20. We requested that each number remain unique and that the numbers be sorted least to greatest. We asked to view the outputted numbers with the markers off. After clicking the “Randomize Now!” button, we obtained the digits 1, 5, and 14. (Of course, when you use the Research Randomizer, you will very likely get a different set of three numbers.) The sample is the TAs labeled 01, 05, and 14. These are Alexander, Gogireddy, and Scarborough.

To use the table of random digits, we might enter Table A at line 116 (any line may be used), which is

14459 26056 31424 80371 65103 62253 50490 61181

The first 13 two-digit groups in this line are

14 45 92 60 56 31 42 48 03 71 65 10 36

We used only labels 01 to 20, so we ignore all other two-digit groups. The first 3 labels between 01 and 20 that we encounter in the table choose our sample. Of the first 13 labels in line 116, we ignore 10 of them because they are too high (over 20). The others are 14, 03, and 10. The sample is the TAs labeled 03, 10, and 14. These are Book, Ozanne, and Scarborough.