ch16 - Chapter 16 Solutions 16.1 This is an experiment...

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Unformatted text preview: Chapter 16 Solutions 16.1. This is an experiment; students were randomly (at the time they visited the site) assigned to a treatment. The explanatory variable is the login box (genuine or not), and the response is the student’s action (logging in or not). 16.2. The population is the 1400 students who participated in counseling. The sample is the 93 students who returned the survey. Note: We might wish to take the population to be all students who ever have or ever will participate in counseling, but our sample was chosen from those who were counseled in the previous semester, and it is probably unreasonable to expect that group to be representative of this larger population. 16.3. (a) Label the students from 0001 to 3478 (or 0000 to 3477). Another possibility is to assign two four-digit labels to each student (for a total of 6956 labels). (b) Taking four digits at a time from line 105 gives 2940, 0769, 1481, 2975, and 1315. If two labels are used for each student, we choose 2940, 0769, 1481, 6077, and 2975. See note on page 54 about using Table B. (c) The response variable is how much money the students earn in the summer. (Presumably, the questionnaire asks some question to get this information—perhaps, “How much did you earn last summer?”) 16.4. Assign labels 01 through 14 to the animals. Using Table B, the animals chosen are 12, 04, and 11. If labels are assigned down the columns, these are (respectively) the barefoot banded gecko, flat-tailed horned lizard, and loggerhead sea turtle. See note on page 54 about using Table B. 16.5. (a) The control group should have 24 trees with no beehives. Diagram is shown below. (b) Label the trees 01 through 72. From line 137 of Table B, the first four active-hive trees are 53, 64, 56, and 68. See note on page 54 about using Table B. (c) The response variable is elephant damage. Random assignment----Á Group 1 24 trees- Treatment 1 active beehive J J J J^- Group 2 24 trees- Treatment 2 empty beehive- J J J J^ Group 3 24 trees- Treatment 3 no beehive----Á Compare elephant damage 185 186 Chapter 16 From Exploration to Inference: Part II Review 16.6. (a) Diagram below. (b) Assign labels 01 through 64. Starting on line 110 from Table B gives the first five chocolate group members as 38, 44, 18, 33, and 46. See note on page 54 about using Table B. Random assignment © ©©* Group 1 32 women- Treatment 1 Chocolate H HHj H HHj Group 2 32 women- Treatment 2 Carob © ©©* Observe headaches in next 12 hours 16.7. (a) Possible response variables: whether or not the subject has a job within some period of time, whether or not the subject stayed in that job, number of hours worked during some period, length of time before subject became employed. For the design, randomly assign about one-third of the group (3355 subjects) to each treatment, and observe the chosen response variables after a suitable amount of time. (b) The simplest approach is to label from 00001 through 10065, and then take five digits at a time from the table. (This meansfrom 00001 through 10065, and then take five digits at a time from the table....
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ch16 - Chapter 16 Solutions 16.1 This is an experiment...

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