Sp Stats Review Worksheet 3 Answers - PowerPoint

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					Correlational Research
& Guidelines for Reading Research

      301 Lab
      Week 2 - Thursday
Agenda for Today:
 1. Turn in observational Method & Results
 2. Discuss correlation & survey methods
 3. Discuss research reading tips
 4. Class survey & data entry using SPSS
 Regarding last week’s homework (observation
  summary, data, & worksheet): I will hold on to that to
  aid me in grading the Methods & Results that you
  did for today.
 Quiz #2 is on Tuesday (6/20). You may have your
  article out during the quiz, as well as any
  notes/books, but be sure to read the article
What are correlations?

   We use correlational research when we
    cannot assign experimental groups due to
    ethics or practicality. For example, smoking
    or gender.
   In correlational research we look to see if one
    variable changes with another (covaries).
   We can also call this an association.

   Assess the relationships among naturally
    occurring variables with the goal of identifying
    predictive relationships.
   *Degree & Direction*

         Is NOT

What statistics do we use with
   There are many statistics available for
    measuring the strength of correlations.

   For this class we will be using pearson
    product moment correlation

   Lower-case r represents Pearson Correlation
    such that…
The formula:

     r=       SP
Where SS = Σ( X – X )2

And SP = ΣXY - ΣX ΣY     n= number of pairs of scores

What do values for r mean?

   r can range from -1 to +1.
   -1 means a perfect negative correlation (as X
    increases, Y decreases)
   0 means there is no correlation (no
    relationship between X and Y)
   +1 means a perfect positive correlation (as X
    increases, Y increases)
                               Negative Correlation
                           How Drinking Predicts GPA
Undergraduate GPA

                           0          2          4            6
                                   Nights Drinking Per Week
                        Positive Correlation
                       How SAT Scores Predict
                         Undergraduate GPA



                       400   600   800   1000 1200 1400 1600
                                    SAT Scores
Other pictures of Scatter Plots
Survey research is correlational

   Characteristics of Surveys include:
       Scope can be limited and specific, or broad and
       Select a representative sample
       Use predetermined set of questions

   Careful selection allows generalizability to
   *remember, our interest= population
   Biased sample: systematically differs from
    the characteristics of the population
   Selection bias: occurs when procedures
    used to select a sample results in over/under
    representation of some segment(s) of the
             Approaches to Sampling

   Nonprobability: does not guarantee that every
    element in the population has an equal
    chance of being included in the sample
       Convenience sampling
   Probability sampling: allows researcher to
    estimate the likelihood that their findings for
    the sample differ from those for the
       Simple random or stratified random sampling
                       Survey Methods

   1) MAIL
       Pros: quick, convenient, no interviewer bias, good
        for “difficult” topics (anonymous)
       Cons: response bias (not everyone does it)
       Increase return rates by:
           “personal touch”
           Min effort is required
           Intrinsic interest of the topic to the respondent
           Identify w/ researcher or sponsor organization
               Survey Methods (cont’d)

   2) Personal interviews
       Pros: more control over administering
       Cons: costly (time/$), interviewer bias
       How can you improve?
           Hire highly motivated, well paid & trained interviewers
           Give detailed instructions for possible situations
           Close supervision
             Survey Methods (cont’d)

   3) Telephone interviews
       Pros: good for brief surveys, less dangerous, no
        problem of physical accessibility, or time.
       Cons: response bias, interviewer bias, cell
        phones, multiple phone households.
       How would you improve a telephone survey?
             Survey Methods (cont’d)

   4) Internet surveys
       Pros: convenient, cheap, large and potentially
        diverse or underrepresented samples.
       Cons: selection bias, response bias, lack of
        control over the research environment.
       What do you think could be done to improve
        internet surveys?
              Survey-Research Designs

   1) Cross-sectional: one or more samples drawn AT
    ONE TIME from the population.
       Describe and predict
   2) Successive independent samples: same
    questions asked of different respondents over a
       Describe changes in attitude/behavior but not how
   3) Longitudinal: same respondents surveyed over
    time in order to look at individuals’ changes
       Hard to identify cause of change
       Threat=Attrition (drop-outs) makes the sample no longer

   Demographic variables: describe
    characteristics of the people who are
   Self-report scales assess
   Accuracy of questionnaires depend on
    careful/expert construction

   Consistency of the measurement
       If you get on a scale 3 times, do you get the same #?
   Increased by:
       1) using many similar items on a measure
       2) testing a diverse population
       3) using uniform testing procedures
   Test-retest reliability method: give same
    questionnaire 2X to large sample.
   Alternate form test
   0.8 reliability needed

   Construct validity: extent to which it measures the
    theoretical construct it’s designed to measure
   Criterion validity: predictive v. concurrent
   Convergent validity: the extent to which 2 similar
    measures correlate with each other in the measure
    of a theoretical construct (p. 174-5).
   Discriminant validity: extent to which 2 measures do
    not correlate with each other in the measurement of
    a theoretical construct.
          Constructing a Questionnaire

   Wording should be clear & specific. Vocabulary
    should be simple & familiar.
   Questions should be short, not leading/loaded,
    should present all conditional info prior to key idea.
    Make sure to check for readability.
       Funnel questions: start broad  specific topic
       Filter questions: general questions asked of respondents to
        see if they need to be asked additional questions (do
        you____? If so, how/why/when/etc?)
   Influence of social desirability: pressure for people to
    respond how they “should” believe not as they
    actually believe (e.g., perhaps participants will try to
    be politically correct).
    Why Correlation Causation Does Not
             Equal Causation
   Correlation: means 2 variables are related
       We can make predictions based on correlations
       We CANNOT infer cause of the relationship
   “Spurious” relationship: when the relation
    between 2 variables can be explained by a
       Correlation, Causation (cont’d)

   It has been found that
    violent crime is
    correlated with ice
    cream sales (as violent
    crime increases, so
    does ice cream sales
    and vice versa). Why is
    this an important
    example of correlation
    not causation?

In thinking about peoples’ attitudes regarding smoking,
   littering, academics, and social honesty, you might
   identify the following attitudes:
   Against smoking cigarettes
   Against littering
   For being socially honest
   For being academically honest

Knowing what you now know about correlation, which do
  you think will be related?
Please take out a piece of paper.
Write your name on the back.

    Answer as truthfully as possible!
Scoring the survey

   Calculate your scores for attitudes towards
    smoking (questions 1, 7, 3,10, 5), littering (6,
    2, 8, 9, 4,) academic honesty (11, 17, 13, 14,
    19) and social honesty (16, 12, 18, 15, 20)
   Assign a 1 to SD, 2 to D, 3 to N, etc.
   Questions marked with R are to be reverse
    scored. So 5 to SD, 4 to D, 3 to N, etc. Or
    just reverse the Likert scale for questions on
    the second half.
   See directions.
Entering Data into SPSS

   Enter titles of the variables into variable view
       For example Smoking, Littering, Academic and
   Enter values for the data in Data View
How to figure out if you want to use an
article for your research
   Skim the article – Six steps:
       1. Read the abstract. If you want to continue, proceed
        to step 2:
       2. Identify the main argument (locate the hypotheses,
        see whether or not they were supported and whether
        there are implications for future work)
       3. Locate the supporting arguments (transitional
        words/phrases will help you find these).
       4. Look for themes – If you see any recurring themes
        across articles, these may be important to the area of
        research. Keep an eye on how each article
        describes/addresses such themes
How to figure out if you want to use an
article for your research (continued)
       5. If you’re still unsure as to what the scope of the
        paper is, then skim other paragraphs as needed
       6. Decide if you want to keep this article as a potential
        article to read “cover to cover.”

   If you’ve determined that an article is worthy of reading
    in its entirety, then you’re ready for the next step–
    reading critically.
Guidelines for Critically Reading Research Articles

    Take your time! If you rush, you will likely miss important
     details. Also, many articles require being read more than once.

    Keep a dictionary nearby – no one knows the definition to
     every word, and looking up unknown words will help you to better
     understand the material. Don’t own a dictionary? I like

    Be a “healthy skeptic” – as you read, thoroughly and carefully
     evaluate the claims being presented (e.g., “Is this the best
     hypothesis for this question?” “Are these results appropriately
     interpreted or is it a stretch?” “Does this idea/theory make
    Write as you read – underline, circle, jot down notes or
     questions in the margins or on a separate piece of paper – your
     opinion of the article matters! You’ll learn much more if you write
     while you read. Also, don’t just underline/highlight. You really
     want to be processing the material as you read.
    Guidelines for Critically Reading Research Articles
   More questions to ask as you read:
       Introduction – What question is being
        addressed (hypotheses)? What sets this
        study apart from the previous research
        reviewed in the intro? Are any key terms
        defined? What answers to these authors hope
        to find (hypotheses)? Does the literature
        review provide acceptable context for the
        research questions?
Guidelines for Critically Reading Research
Articles (continued)
     Method – Who participated? How were the
      variables of interest operationalized? Is there
      a control group? If not, is there an
      explanation? Does it make sense?...Were the
      participants selected, sampled, randomly
      assigned to groups? Do they represent some
      larger population of interest? Large enough
Guidelines for Critically Reading Research
Articles (continued)
     Results – Is there evidence that any manipulations
      and/or measures worked – what kind of evidence is it?
      Were the main hypotheses supported? What were the
      main findings? Even if you are unfamiliar with the
      statistics used, can you understand the way that
      the results of the stats are described? Do the
      tables/figures help?
Guidelines for Critically Reading Research
Articles (continued)

   Discussion – In what way(s) does the study add to what we
    already know about the topic or question? If the study
    answered any questions, what were they? Did the study
    lead to any new questions – which? What are the practical
    implications of the findings? What were the study’s
    limitations? What studies should be conducted next? Do
    the authors’ implications make sense? Are they
    reasonable, or do they stretch the results? How could the
    study be improved? What changed would you make?

   Note: These questions are also helpful in writing and revising
    your own papers!

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