Data (copy and paste into statcrunch)Subject Depr-Caf Depr-NC Fatig-Caf Fatig-NC Focus-Caf Focus-NC Smoker Caffeine Change in Depr1 5 16 5 28 23 1 Y 2548 112 5 23 16 20 25 12 N 231 183 4 5 9 5 9 11 Y 642 14 3 7 3 23 13 2 N 1029 45 8 14 0 4 17 10 N 302 66 5 24 1 27 30 20 N 430 197 0 6 5 13 15 2 N 342 68 0 3 3 2 19 19 Y 295 39 2 15 0 28 28 27 N 371 1310 11 12 7 17 13 2 N 270 111 1 0 25 7 4 21 N 516 -112 0 7 10 15 23 20 N 532 713 0 4 20 28 30 10 N 592 414 1 2 18 19 23 21 N 307 115 1 6 6 16 26 24 N 483 516 1 8 2 4 22 24 Y 480 717 8 13 2 6 10 6 N 804 518 5 20 10 16 8 10 Y 705 1519 6 22 6 18 15 13 N 580 1620 8 16 0 3 18 15 N 597 821 3 13 1 5 16 14 Y 364 1022 6 16 3 3 19 15 N 403 1023 0 3 6 20 20 10 N 289 324 3 4 7 10 25 20 Y 302 125 4 5 3 5 19 19 N 403 126 2 3 6 8 15 10 N 260 127 2 2 4 4 15 10 N 732 028 4 5 13 16 30 25 N 347 129 6 7 12 13 9 10 Y 379 130 5 9 10 23 20 17 N 482 4

Variable Name Description of Variable UBJECT Subject number (a whole number from 1 to 40), EPR-CAF Depression score during caffeine period, EPR-NC Depression score during no-caffeine period, ATIG-CAF Fatigue score during caffeine period, ATIG-NC Fatigue score during no-caffeine period, FOCUS-CAF Concentration/focus score during caffeine period, OCUS-NC Concentration/focus score during no-caffeine period, SMOKER Smoker status (Y if smoked cigarettes daily, N otherwise), CAFFEINE Daily intake of caffeine (in mg), CHANGE IN DEPR Change in depression score (Change = Depr-NC - Depr-Caf). Jse the data provided to answer the following questions: First you will examine the experiment design. (a) Can we treat the 30 subjects who agreed to participate in the study as a random sample from the population of all caffeine-dependent individuals? Explain why or why not. Can you generalize the results of the study to the population of all caffeine-dependent individuals? Explain briefly. (b) Why were both the subjects and the experimenters interviewing the subjects blinded to whether the subject was receiving the caffeine pills or the caffeine-free pills? (c) Why was the order in which the two series of capsules were taken randomized? (d) Why were the two study periods held one week apart instead of using two consecutive 2-day periods