1. Thinking Critically with Psychological Science Chapter 1
Psychology 7e in Modules

2. Exploring Cause and Effect Evaluating Therapies
Thinking Critically …
Experimentation
Exploring Cause and Effect
Evaluating Therapies
Independent and Dependent Variables

3. Experiments isolate causes and their effects.
Experimentation
Exploring Cause and Effect
Like other sciences, experimentation is the backbone of psychology research.
Experiments isolate causes and their effects.
OBJECTIVE 12| Explain how experiments help researchers isolate cause and effect.
Psychology 7e in Modules

4. Exploring Cause & Effect
Many factors influence our behavior. Experiments (1) manipulate factors that interest us, while other factors are kept under (2) control. Effects generated by manipulated factors isolate cause and effect relationships.
It’s a joke!!!
Cause and effect relationship???
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5. Independent Variable v Dependent Variable
An Independent Variable is a factor manipulated by the experimenter. The effect of the independent variable is the focus of the study. (An independent variable is the presumed cause; …..) or (What I change; …) They need to be MEASURABLE.
A Dependent Variable is a factor that may change in response to an independent variable. In psychology, it is usually a behavior or a mental process. (… the dependent variable is the presumed effect.) (…what I observe.)
They need to be MEASURABLE.
OBJECTIVE 14| Explain the difference between an independent variable and a dependent variable.
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6. Dependent v Independent Variables
Memory rule:
The dependent variable depends on the independent.
You always hope to change the dependent by altering the independent.

7. Independent Variable v Dependent Variable
The following is a hypothesis for a study. “There will be a statistically significant difference in graduation rates of at-risk high-school seniors who participate in an intensive study program as opposed to at- risk high-school seniors who do not participate in the intensive study program.” (LaFountain & Bartos, 2002, p. 57) IV: Amount of time spent in participating in intensive study program. DV: Graduation rates.

8. Dependent v Independent Variables
Of 100 individuals with obsessive- compulsive disorder (OCD), 50 receive 8 weeks of an experimental drug for OCD, while 50 are placed on a waiting list for 8 weeks. At the end of the 8 weeks, all 100 individuals are given psychological tests to assess their level of OCD.
What is the :
Independent Variable
Dependent Variable?
Experimental Condition?
Control Condition?
What are two operational definitions?
IV is treatment received – the drug DV is the OCD EC those receiving the drug CC those who did not receive the drug
Psychology 7e in Modules

9. Double-blind Procedure
Evaluating Therapies
Blind Procedure
The participants are uninformed about what treatment, if any, they are receiving. (Experimental Group - treatment v Control Group - placebo)
Double-blind Procedure
In evaluating drug therapies, patients and experimenter’s assistants should remain unaware of which patients had the real treatment and which patients had the placebo treatment.
OBJECTIVE 13| Explain why random assignment and double-blind procedure build confidence in research findings.
Psychology 7e in Modules

10. Charlatans – The Power of Suggestion

11. Evaluating Therapies Random Assignment
Assigning participants to experimental (Breast-fed) and control (formula-fed) conditions by random assignment minimizes pre-existing differences between the two groups.
Sometime research participants out of enthusiasm or personal beliefs can affect the out come of an experiment. To control for such affects, a double-blind procedure is used, in which the participants and the experimenter’s assistants are not aware of which participants got real treatment and who got placebo.
Psychology 7e in Modules

12. A summary of steps during experimentation.

13. Below is a comparison of different research methods.
IMPORTANT!!!!!!!
Below is a comparison of different research methods.

14. Statistical Reasoning
Statistical procedures analyze and interpret data allowing us to see what the unaided eye misses.
OBJECTIVE 15| Explain the importance of statistical principles, and give an example of their use in daily life.
Composition of ethnicity in urban locales
Psychology 7e in Modules

15. Describing Data
A meaningful description of data is important in research. Misrepresentation may lead to incorrect conclusions.
OBJECTIVE 16| Explain how graphs can misrepresent data.
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16. Measures of Central Tendency
Mode: The most frequently occurring score in a distribution. Mean: The arithmetic average of scores in a distribution obtained by adding the scores and then dividing by the number of scores that were added together. Median: The middle score in a rank- ordered distribution.
OBJECTIVE 17| Describe three measures of central tendency and tell which is most affected by extreme scores.
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17. Measures of Central Tendency
A Skewed Distribution

18. Salaried Salespeople $20,000 $25,000 $35,000 $200,000
What is the mode?
What is the median?
What is the mean?
In this instance, why is the mean not the best estimate of what a salesperson would earn?

19. Measures of Variation
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.
OBJECTIVE 18| Explain two measures of variation.
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20. Variability
Variability refers to how much the scores in a data set vary from each other and the mean. The standard deviation is an index of the amount of variability in a data set. When variability is great, the standard of deviation will be relatively low. When variability is low the standard of deviation will be smaller. Estimates of variability play a crucial role in deciding whether the results of a study support a researchers hypotheses.

21. Standard Deviation

22. Thinking Critically … Statistical Reasoning Describing Data
Making Inferences

23. When is an Observed Difference Reliable?
Making Inferences
A statistical statement of how frequently an obtained result occurred by experimental manipulation or by chance.
When is an Observed Difference Reliable?
Representative samples are better than biased samples.
Less variable observations are more reliable than more variable ones.
More cases are better than fewer cases.
Psychology 7e in Modules

24. When is a Difference Significant?
Making Inferences
When is a Difference Significant?
When sample averages are reliable and the difference between them is relatively large, we say the difference has statistical significance. For psychologists this difference is measured through alpha level set at 5 percent.
OBJECTIVE 20| Explain how psychologists decide whether differences are meaningful.
Psychology 7e in Modules