Research methods FEATURES An independent variable IV is

Research methods

FEATURES • An independent variable (IV) is manipulated • A dependent variable(s) (DV) is measured • Many basic experiments consist of two levels of the independent variable • experimental group • control group • Control over extraneous variables • holding constant • randomizing effects • A causal relationship between the independent and dependent variables can be established Experimental research

CHARACTERISTICS • Subjects are randomly assigned to research groups • A given participant must be equally likely to be assigned to any of the given groups • Random number table • Flip a coin • In experimental designs, a causal relationship between the independent and dependent variables can be established Experimental research

VARIABLES • Differing values of the IV are called “levels” • May vary quantitatively (numerical data) o 10 mg day o 20 mg day e. g. here are 2 levels of variable dosage • May vary qualitatively (descriptive data) o Zoloft o Imipramine o Prozac e. g. here are 3 levels of the variable medication type Variables

• An operational hypothesis is a clearly defined set of procedures for measuring or manipulating the construct of interest. • The key to an acceptable operational hypothesis is that the procedure is specified precisely enough to allow replication by others. Examples quality of memory -- accuracy of recall in a certain task depression -- Beck Depression Inventory (survey) score arousal -- galvanic skin response (conductivity of the surface of the skin) Operational hypothesis

She is a good car salesperson Verbal statement She: 1. Sells many cars 2. Points out +ve features 3. Is nice 4. Sells only good cars Operational hypothesis

1. Environment/Number of stressors a) Number negative life events b) Number of examinations Stress 2. Self-report a) Measurable nervous mood 3. Behaviour a) Number of fidgets/minute b) Psychophysiological responses elevated Verbal statement Operational hypothesis

• Social loafing refers to people’s tendency to slack on group tasks. In one study on social loafing, college participants cheered alone and in groups of 2, 4 or 6 people. They were told to cheer as loud as possible at specific times so researchers could determine how much noise people made in social settings. The amount of noise made by each participant dropped as group size increased. 1. What is the IV? 2. What is the DV? 3. Why is random assignment important here? Identify Key Experimental Features