Question

Dr. Brierly is interested in the impact of competition on aggressive behavior in capuchin monkeys. Based on previous research, it is thought that the primary role of aggression is to reduce competition for limited resources. Dr. Brierly predicts that monkeys that live in larger groups will exhibit higher levels of aggressive behavior. The monkeys are normally housed in an outdoor lab space in groups of 5. He randomly assigns all animals to 3 new groups that he calls Large, Medium, and Small, which vary in regards to group size. He then observes their behavior at feeding time, and tallies the total number, as well as the degree of (low, moderate, and high) aggressive interactions. After data collection (and despite random assignment to groups), he realizes that the majority of the monkeys in the Large group are young adults, whereas those in the Medium and Small groups are older animals.

1. What is Dr. Brierly’s hypothesis?
2. What is the Independent Variable (IV), and how do you know this?
3. What is the Dependent Variable (DV), and how do you know this?
4. What confounding variable is apparent, and why might it be a problem?
5. What scale of measurement is the IV, and how do you know this? (i.e., nominal, ordinal, interval, ratio)
6. Dr. Brierly measures the DV in two ways. To what scale of measurement do each of these belong, and how do you know this? (i.e., nominal, ordinal, interval, ratio).
7. After finishing his current study, Dr. Brierly decides to run it again, but adds an additional variable, which is type of food offered. Diet A consists of monkey biscuit (a staple diet) and fruit (a real favorite for the monkeys), while diet B consists of monkey biscuit and vegetables. Diet C consists of monkey biscuit only. What type of variable is this (IV, DV, Subject), and what is the scale of measurement? Please make sure to explain your answer.

Answer 1

Dr. Brierly’s hypothesis
Dr. Brierly believes that competition affects the aggressive behavior in capuchin monkeys.

Independent Variable (IV)

IV: Group size: Large, Medium, and Small. Since we want to see the effect of group size(competition) on the behavior of monkeys, group size is independent.

Dependent Variable (DV)
DV: the degree of (low, moderate, and high) aggressive interactions Because the behavior of monkeys depends on group size.

confounding variable
The age might be the possible confounding variable which can cause the changes in aggressiveness in different sized groups.

IV Level of measurement: Ordinal level of measurement. Since group size classified into a number of labels (qualitative in nature) and the groups are ordered in terms of Large, Medium, and Small, this is an ordinal level of measurement.

Dependent Variable (DV)
Level of measurement: Ordinal level of measurement. Since aggressive behavior classified in terms of the degree of aggressive interactions, i.e. low, moderate, and high which are qualitative in nature and can be ordered in terms of high or low degree of interaction, this is an ordinal level of measurement.

Type of food: this is an independent variable because this is independently chosen and we want to see the effect of type of food on the aggressive behavior of monkey.
Level of measurement: Nominal level of measurement. Since the data values are classified into number of labels (qualitative in nature) such that Diet A, B or C, this is a nominal level of measurement.