Psych 218 Introduction to Behavioral Research Methods

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Psych 218Introduction to Behavioral Research
Methods

• Week 8 Lecture 16

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Outline of Todays Lecture

• Last lecture we discussed
• Correlation and regression
• Hypothesis testing
• Today we will discuss
• Hypothesis testing
• Representing variable and confidence intervals in
  graphs
• Writing research reports

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Null-Hypothesis Testing and Inferential Statistics
True State of the World
2 realities by 2 decisions form a 2 x 2 matrix of
4 possibilites
Decision
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Null-Hypothesis Testing and Inferential Statistics

• How do we infer whether to reject the null
  hypothesis and conclude that a relationship does
  indeed exist?
• Inference the act of deriving a conclusion from
  facts or premises
• Inferential Statistics statistical tests that
  estimate the probability of a Type I error
• Type I error is an incorrect rejection of the
  null hypothesisyou think the differences in the
  data indicate an effect is there, but in reality
  any differences are due to noise

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Null-Hypothesis Testing and Inferential Statistics

• The probability of a Type I error is generally
  expressed as p
• Inferential statistical tests (t-tests, ANOVA,
  correlation, regression) are designed to estimate
  p
• Low values of p suggest that it is highly
  unlikely that the differences in the data are due
  to random variability alone ? a relationship
  between the variables likely exists!
• In many sciences, researchers as a group have set
  a criterion by which to judge p a .05

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Representing Data Graphically

• Scatterplots vs. Plots of means

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Placebo Treatment
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Placebo Treatment
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Representing Dispersion in Data Graphically

• Error bars on graphs
• Standard deviation, s
• Standard error of the mean (se or )
• Confidence intervals (CI)
• Assume data is normally distributed
• 95 CI 1.96
• CI represents boundaries of that account for 95
  of distribution

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Representing Dispersion in Data Graphically

• Plots of means with error bars
• error bars /- 1 se error bars /- 95 CI

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Placebo Treatment
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Placebo Treatment
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Representing Data Graphically

• Boxplots
• Five-Number Summary
• Lowest value (Q0?), Q1, Q2, Q3, Highest value
  (Q4?)

Outlier value
90th percentile
Q3 75th percentile
Median (Q2 or 50th percentile)
Q1 25th percentile
10th percentile
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Placebo Treatment
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Writing a Research Proposal and Report

• Purpose of Research Proposal
• Presents a literature review that defines the
  concepts and variables pertinent to a particular
  research question
• Presents a specific research question with
  explicit hypotheses to be tested
• Develops a plan for addressing that research
  question empirically, including descriptions of
• Target population and subject sampling
• The research design, including explicit
  definition of independent and dependent variables
  and how the stimuli and procedures implement
  these variables
• Aspects of stimuli and procedures that help to
  control for extraneous variables and confounding
  variables
• Types of analyses to be used, predicted results,
  and how these predictions relate to the hypotheses

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Writing a Research Proposal and Report

• Purpose of Research Report
• Present the results of empirical research and
  places them in the context of previous research
• Contains all elements of research proposal (see
  previous slide) plus
• The research report presents the results and
  analyses
• The research report discusses the results to
  place them in context

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Research Proposals and Reports Global Concerns

• Scientific Writing Style
• Precision more important than entertainment, but
• Research is part science and part advertising
  not only do you need to develop good ideas but
  you must be able to sell your ideas
• Proposal is often the basis of first impression
  for the quality of the research project
• Proposal must be clear on ALL levels of analysis
• Words
• Sentences
• Paragraphs OUTLINE!
• Sections

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Research Proposals Global Concerns

• APA guidelines
• Orderly expression of ideas - organization
• Smoothness of expression - transitions
• Economy of expression - concise language
• Precision and clarity use scientific vocabulary
  jargon correctly and insure that all terms are
  defined the first time they are used

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Organization of Research Reports and Proposal
USE APA STYLE!

• Title Page title should specifically describe
  what the paper is about so that it is useful
  information for other researchers literature
  searches
• Abstract
• essentially a mini-paper for lit. searches
• be extremely CONCISE! (lt 150 words)
• introduce specific topic
• discuss variables, etc.
• present major results (no statistics!)
• discuss important conclusions

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Organization of Research Reports and Proposal
USE APA STYLE!

• Introduction
• Purpose
• Demonstrate knowledge of relevant research
• Define intervening variables and their relation
  to manipulations and measurements used in
  previous reserach
• Present and justify research question and
  hypotheses
• Present and justify the general method to be used
• Organization
• Start broad then narrow to your general purpose
• Discuss only relevant research in a logical flow
• Near the end provide an explicit statement of
  hypotheses and an overview of the general
  research design

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Organization of Research Reports and Proposal
USE APA STYLE!

• Method
• explicitly state how variables are manipulated
• define in separate sub-sections
• Participants (subjects)
• Design
• Stimuli/Apparatus/Materials
• Procedures
• Results
• scales of IVs and DVs
• transformations of DVs
• list analyses you plan to perform
• summarize predictions

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Things to Avoid Dr. Dyres Pet Peeves

• Use of informal language e.g., you dont run
  subjects, you test participants
• Ambiguous pronouns if you use the word it make
  sure the surrounding context makes the meaning of
  the word it obvious, otherwise avoid using it
  (as in it)
• Sexist pronouns (he vs. she) word sentences to
  avoid having to use these if at all possible, or
  use he or she
• Verb tense
• Introduction Section discussion of specific
  previous research ? past tense, ideas or concepts
  that are general for all time and not linked to
  past? present tense
• Method and (predicted) results
• future tense for proposals
• past tense for reports

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Things to Avoid Dr. Dyres Pet Peeves

• Plural/singular mismatches
• Passive voice word sentences in active voice
• Passive voice subject of the sentence receives
  the action of the verb
• The President was elected by the citizenry
  The fish was caught by the boy
• Active voice subject of the verb carries out
  some action
• The citizenry elected the President The boy
  caught a fish
• Superfluous, imprecise language (e.g., avoid
  vague adverbssearch for all words ending in ly
  and consider eliminating them)
• Style issues like that vs. which