Scientific Methodology in Psychology

The Scientific Method rules for conducting research prescribed methodology for the collection, analysis and interpretation of data

Why use the scientific method? reduces chances for error provides procedures for repeatability and subsequently, reliability self correcting

Basic Steps for Conducting a Scientific Experiment Observe and Identify the Problem (ask a question) Formulate an Hypothesis this is a statement of your question and a guess about the answer Design the Experiment operationally define variables, select and assign subjects,

Conduct the Experiment (collect data) Analyze and Interpret Data utilize statistical analysis to determine significance *Report Findings (publish data) *Why is this last step so important?

Consider the following example:

Observations observations of school children and surveys concerning preferred breakfasts indicate that children eating sugar sweetened cereals performed better on standardized tests throughout the day observations of animals in learning tasks show that those eating Froot Loop cereal learned to solve the maze in less time than those receiving non-sweetened food reinforcers

Hypothesis Consuming sugar enhances memory Where did this hypothesis come from?

Observation in animal experiments and humans in natural environment Logical progression of information from other fields or other areas of the same field

Design and Conduct Experiment Dependent Variable (DV) = that which the experimenter measures Independent Variable (IV) = that which the experimenter manipulates Operational Definition (OD)= the exact procedure used to measure an intangible variable

Must be randomly selected and randomly assigned to either: Subjects: Must be randomly selected and randomly assigned to either: Experimental Group (E) those subjects who receive the treatment Control Group (C) those subjects who receive a placebo What does "random" mean as used here?

Which group receives sugar? Which group receives saccharine? We want to give some students sugar and others a placebo (saccharine) and test their ability to recall a list of nonsense syllables. What is our DV? What is the OD of our DV? What is our IV? How many levels of the IV are there? Which group receives sugar? Which group receives saccharine?

Controlling Error Extraneous Variables conditions which might affect the outcome but can be controlled by the experimenter. What are some possible extraneous variables in our experiment? Why did we have the control group consume saccharine? Why not have them consume nothing at all?

confounding variable uncontrolled extraneous variables which render results invalid what are some possible confounding variables in each of our experiments?

Experimental Design Single Blind Experiment The subjects are unaware of the group to which they belong Can control subject bias self-fulfilling prophecy

Double Blind Experiment Neither the subjects nor the experimenter know to which group the subjects belong Can control experimenter effects

Results: Fifty students were randomly assigned to the either the experimental (sugar sweetened water) or control (saccharine sweetened water)group. After consuming 8 oz. of the drink, the students were given a list of 50 nonsense syllables to memorize for 1 hour. They were then given a math task to control for rehearsal effects. The number of nonsense syllables each recalled after 1 hour was measured. Results were as follows: Experimental Mean # recalled = 33 Control Mean # recalled = 24

What can we conclude from our data? Note: although it appears to support our hypothesis, we must conduct statistical analyses to determine if effect is true or occurred just by chance alone

True Experiment Example represents true experiment because IV is controlled and subjects are randomly assigned Allows us to draw causal conclusions.

Inferential vs Descriptive Statistics inferential statistics use sample data to draw conclusions about the population experimental designs allow us to draw causal conclusions about the population descriptive statistics numerical values that summarize sample data

Descriptive Statistics Measures of Central Tendency Mean (the average score) Median (the middle score) Mode (the most frequently occurring score) Skewed distributions Negative/Positive Measuring Variability Standard Deviation

An Observational Study How long do people wash their hands after using the bathroom? You observe approx. 50 subjects over the course of 3 days You time each subject’s hand washing You report your findings

So would you say that knowing the average gives you sufficient information on which to make a decision? e.g. The average number of hours of study necessary to get an A is 3 per week e.g. On average, you have to “crash” the toll booth 5 times before you’ll get a ticket

Positive Skew Mean is higher than the median

Negative Skew Mean is lower than the median

Correlational Studies

Correlational Studies provide information about the relationship between two variables can be used to make predictions cannot be used to draw causal conclusions

Why conduct correlational studies? Why not conduct experiments?

Consider the following examples: relationship between IQ and income race and traffic tickets weight and incidence of diabetes blood cholesterol levels heart attacks cigarettes smoked and incidence of lung cancer note that these are variables which cannot be randomly assigned for practical or ethical purposes

Correlations may be: Direct or Positive Correlation As A increases, B increases Indirect or Negative Correlation As A increases, B decreases

negative positive B B A A no correlation B A

Negative Correlation Positive Correlation No Correlation

Correlation Coefficient indicates degree and direction of relationship most common is the Pearson r values range from -1 0 +1 cannot be < -1 cannot be > +1 0 = no correlation

Which provides more information, a negative correlation or a positive correlation? What does a correlation coefficient of -1.4 indicate? Why can’t we draw causal conclusions from such data?

Great care must be taken when considering the applicability of correlational studies to the general population. errors in sampling can lead to incorrect conclusions: Sigmund Freud 1948 Presidential Election XYY males and violent behavior

"Other Types of Research"

Single Subject Design can be correlational or experimental case studies most common type observation and testing of an individual with unusual characteristics such as disease or injury eg. Phineas Gage eg. Patient HM

Phineas Gage

Pt. H.M.

Naturalistic Observation observations of humans or other animals in their natural environment observer effects problem people change their behavior when they know they're being watched Dr. Jane Goodall