1. Research Strategies: How Psychologists Ask and Answer Questions
Chapter 1
Research Strategies: How Psychologists Ask and Answer Questions

2. Two Random Sequences
Your chances of being dealt either of these hands is precisely the same: 1 in 2,598,960.

3. Experimentation Experiment
an investigator manipulates one or more factors (independent variables) to observe their effect on some behavior or mental process (the dependent variable)
by random assignment of participants the experiment controls other relevant factors

4. Experimentation Double-blind Procedure Placebo effect
both the research participants and the research staff are ignorant (blind) about whether the research participants have received the treatment or a placebo
commonly used in drug-evaluation studies
Placebo effect
experimental results caused by expectations alone
any effect on behavior caused by administration of an inert substance or condition, which is assumed to be an active agent

5. Experimentation Experimental Condition Control Condition
the condition of an experiment that exposes participants to the treatment, that is, to one version of the independent variable
Control Condition
the condition of an experiment that contrasts with the experimental treatment
serves as a comparison for evaluating the effect of the treatment

6. Experimentation Random Assignment
assigning participants to experimental and control conditions by chance
minimizes pre-existing differences between those assigned to the different groups

7. Experimentation Independent Variable Dependent Variable
the experimental factor that is manipulated
the variable whose effect is being studied
Dependent Variable
the experimental factor that may change in response to manipulations of the independent variable
in psychology it is usually a behavior or mental process

8. Experimentation

9. Statistical Reasoning
Our Brand Brand Brand
Brand X Y Z
100% 99 98 97 96 95
Percentage
still functioning
after 10 years
Brand of truck

10. Statistical Reasoning
Our Brand Brand Brand
Brand X Y Z
100% 90 80 70 60 50 40 30 20 10
Percentage
still functioning
after 10 years
Brand of truck

11. Statistical Reasoning
Mode
the most frequently occurring score in a distribution
Mean
the arithmetic average of a distribution
obtained by adding the scores and then dividing by the number of scores
Median
the middle score in a distribution
half the scores are above it and half are below it

12. Statistical Reasoning
A Skewed Distribution 90
475
710 70
Mode Median Mean
One Family
Income per family in thousands of dollars

13. Statistical Reasoning
Range
the difference between the highest and lowest scores in a distribution
Standard Deviation
a computed measure of how much scores vary around the mean
Statistical Significance
a statistical statement of how likely it is that an obtained result occurred by chance