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

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

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. http://4.bp.blogspot.com/_qUFDMUpk9jE/SamaufWnPRI/AAAAAAAAP1c/AzyqEfgYdPA/s400/bizarro-animal-experimentation.jpg Psychology 7e in Modules

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!!! http://www.702communications.com/~ahill/Cause%20and%20effect%20perhaps.jpg Cause and effect relationship??? Psychology 7e in Modules

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. Psychology 7e in Modules

Dependent v Independent Variables Memory rule: The dependent variable depends on the independent. You always hope to change the dependent by altering the independent.

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. http://www.uncp.edu/home/collierw/ivdv.htm

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 http://answers.yahoo.com/question/index?qid=20080127143317AAIw38P Psychology 7e in Modules

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

Charlatans – The Power of Suggestion

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

A summary of steps during experimentation.

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

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

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. Psychology 7e in Modules

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. Psychology 7e in Modules

Measures of Central Tendency A Skewed Distribution

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?

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. Psychology 7e in Modules

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.

Standard Deviation

Thinking Critically … Statistical Reasoning Describing Data Making Inferences

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

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