Reasoning in Psychology Using Statistics Psychology 138 Spring 2015

Reasoning in Psychology Using Statistics Announcements Added some tutorial videos authored by Dr. Joel Schneider in the Resources and Materials section of ReggieNet.

Reasoning in Psychology Using Statistics What are Statistics? “It’s about almost everything in modern society.” Bennett, Briggs, Triola (2003), Statistical Reasoning for Everyday life

Reasoning in Psychology Using Statistics What are Statistics? “It’s about almost everything in modern society.” Bennett, Briggs, Triola (2003), Statistical Reasoning for Everyday life Statistics: tools, used to make data based decisions –Descriptive statistics –Inferential statistics Data: numbers with a context –How were numbers measured, what do they mean?

Reasoning in Psychology Using Statistics Ways of knowing “The world of statistics starts with a question, not with data” Keller 2006, Tao of Statistics Traditional knowing: truth or error –Assumes perfect uniformity –Assumes error-free repetitions Modern knowing: probabilistic –Assumes variability Our focus: Scientific Method –Systematic observation (& experimentation) used to explain how and why events occur Systematic observations constitute data Statistics are used to describe data & relationships within data T r u

Reasoning in Psychology Using Statistics The research process Scientific Method –Ask research question –Identify variables and formulate hypotheses –Define population –Select research methodology –Collect data from sample –Analyze data –Draw conclusions based on data –Repeat Statistics

Reasoning in Psychology Using Statistics An Example How test claim scientifically? What data to collect? Who to test? How do we make our observations? Claim: Absence makes the heart grow fonder ?? –But, what about your observation that long distance romances never work out? (Out of sight, out of mind)

Reasoning in Psychology Using Statistics Variables What data do we collect? –Identify what we are studying Variables –Characteristics or conditions that change or have different values for different individuals (or situations) –Independent (explanatory) variables (IV) »Variable that has causal impact »In experiment, variable that is manipulated by researcher –Dependent (response) variable (DV) »Variable observed for changes to assess effect of the manipulation in an experiment »Variables measured in observational research

Reasoning in Psychology Using Statistics Independent and Dependent Variables Absence makes the heart grow fonder –What are some potential Independent (explanatory) variables? How long apart? How far apart? How much communication? How “strong” was the relationship to begin with (quasi-independent)? –What are some potential Dependent (response) variables? Ratings of fondness for partner Heart rate when seeing a picture of partner fMRI of brain when hearing partner’s voice ??

Reasoning in Psychology Using Statistics Experimental Unit What is the level at which the research is focused? –Individuals Between individuals Within individuals –Across groups Couples Families Cities Ethnic groups Our example: Absence makes the heart grow fonder – What level(s) could we focus on?

Reasoning in Psychology Using Statistics Getting experimental participants Who to test? –Population Set of all individuals of interest – Sample Subset of population data collected from Typically no access to whole population Test sample & generalize results to population as a whole

Reasoning in Psychology Using Statistics Basic Research Methods Absence makes the heart grow fonder How could we go about testing this? What data should we collect? Who should we test? How should we make our observations? –Observational study Observe & measure variables of interest to find relationships No attempt to manipulate or influence responses –Experimental methodology Independent variable manipulated while changes observed in another variable (dependent) Can establish cause-and-effect relationships Extensive controls to minimize extraneous sources of variability –Quasi-experimental methodology One (or more) of the independent variables is a pre-existing characteristic (e.g., sex, age, etc.)

Reasoning in Psychology Using Statistics What are Statistics? Statistics: tools, used to make data based decisions Data: numbers with a context –Understanding the context in which the observations are made (e.g., How were numbers measured? Who did they come from? What do they mean?) is critical for both doing statistical analyses as well as interpreting the results. “The world of statistics starts with a question, not with data” Keller 2006, Tao of Statistics

Reasoning in Psychology Using Statistics Today’s Lab Learning the basics of SPSS including entering data

Reasoning in Psychology Using Statistics Brief tour of SPSS Two view windows: To switch between the views click on the tabs

Reasoning in Psychology Using Statistics The Variable View This is where you specify the details about the variables Each column corresponds to a feature of the variables Each row corresponds to a variable

Reasoning in Psychology Using Statistics The Data View So each column in the data view corresponds to a row in the variable view Each column corresponds to a variable Each row corresponds to an experimental unit (called “ cases ” in SPSS lingo)