Indicate whether each variable below is (most likely) manipulated or measuredHomework 4- Student Rubric

1. Indicate whether each variable below is (most likely) manipulated or measured. (3 points)

• number of siblings each participant has
• how long a participant is given to complete a task: 30 minutes, 20 minutes, or 10 minutes
• how long a participant takes to complete a task
• participant’s score on an anagram test
• level of test participants receive: easy or difficult
• level of test participants choose to take: easy or difficult
• whether a participant has worn braces
• personality of the experimenter: friendly or stern

2. Read the following examples labeled. After you have read them, write down the following:

a. Each of the following examples, except one, has an internal validity problem. Identify the one example that does not have an internal validity problem. (2 points)
b. For the remaining examples (with internal validity problems), identify whether the problem is a design confound, a selection effect, or an order effect and explain why (2 points).
c. Finally, explain how each of the problematic studies might be changed so that it does not have the internal validity problem. Mention at least one fix for each of the examples and why that change would help. (4 points).

Example 1

An applied psychologist wants to test the effectiveness of an intervention to increase awareness of the environmental impact of disposable water bottles. The initiative involves asking students to use a smartphone to track the number of disposable water bottles they use, categorizing whether they reuse them, throw them away, or recycle them. He asks for volunteers in a large geology course. Students must own a smartphone in order to participate in the intervention group. Fifty volunteers who owned a smartphone were assigned to the tracking condition (they downloaded a free smartphone app for this purpose). Fifty more students who were interested, but who did not own a smartphone, made up the comparison group. This group was simply exposed to a short video on the impact of plastic water bottles. At the end of a two-week period during which the students in the smartphone group tracked their water bottle use, the researcher found that students in the tracking program were more likely to have purchased a reusable water bottle in the past week compared with the students in the comparison group. He concluded that his smartphone tracking program raised awareness, causing students to purchase reusable bottles.
Example 2

cognitive psychologist believes that people learn better when they spread out their studying over several days, so she creates a study with three groups of participants. Each group studies the same list of 120 Chinese vocabulary words (none of the participants had studied Chinese before). One group studies the words for 20 minutes on the first day. The second group studies the words for 20 minutes on the first and second days. The last group studies the words for 20 minutes on the first, second, and third days. On the fourth day, all of the participants are tested on how well they have learned the Chinese vocabulary words. The people in the last group scored the best, so the researcher concludes that distributed studying does improve people’s ability to learn.
Example 3

A human factors psychologist is comparing visibility features for automobiles. (Human factors psychologists study how humans interact with the material world.) He plans to test whether drivers will avoid obstacles behind their cars more effectively when the car is equipped with an enhanced rearview mirror, a rear video camera system, or an object detector that sets off a buzzer alarm. He randomly assigns the 25 drivers into the cars (one with an enhanced rearview mirror, one with a rear video camera system, and one with an object detector that sets off a buzzer alarm) . The cars are identical except for their object detectors. The drivers spend 1 hour familiarizing themselves with their vehicles and their object detectors by running through a set of drills on a closed driver’s course. During a test phase, the researcher places a set of objects behind each driver. The test objects range in height, color, and movement. Each driver attempts to back up his or her car while avoiding each of the test objects. Each object is presented three times each. The psychologist finds that, on average, drivers respond more accurately to the rear camera video system compared to the rearview mirror or the buzzer alarm.

3. Bruce is conducting a within-groups experiment in which people are going to taste pretzels, popcorn, and candy canes and rate each snack on a nine-point scale.

a. What kind of design is this: Repeated measures or concurrent measures? Identify which one it is and briefly explain why. (2 points)
b. Why should Bruce use counterbalancing in his design? (2 point)
c. How should Bruce set up his counterbalancing to be sure he has presented all possible orders of the independent variable conditions? (2 points)
d. What if Bruce decided to add two more snacks to his design, tortilla chips and raisins? How would these additions affect his counterbalancing plan? Mention at least 1 pro of this counterbalancing and at least 1 cons of this counterbalancing plan (3 points).