Research Design

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Research Design Analysis 1Class 11

• Announcements
• answer key online
• web pages
• http//plato.acadiau.ca/COURSES/PSYC/McLeod/2013-9
  9/Assignments/assign2studentpages.htm
• Chapter 11 descriptive statistics today (lab)

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Sources of distortion?

• Instruments (measures)
• Sampling
• Observer bias
• biggest problem with behavioral coding
• observer is part of measuring instrument
• power of inference

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Inter-rater reliability Percent agreement
Percent agreement
Total number of agreements x 100 Total number of
observations
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Inter-rater reliabilityCohens Kappa
Cohens Kappa
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Cohens Kappa Confusion matrix
Cohens Kappa
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Cohens Kappa Correcting for chance
Cohens Kappa
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Inter-rater reliability with interval data
Pearsons product-moment correlation r 1.0
But dont agree on any! If use, need mean
st.dev.
M 3.2 5.2 SD 2.0 2.0
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Naturalistic observations

• Unobtrusive
• blinds, mirrors, cameras
• Purely descriptive
• High external validity
• also
• Participant observation
• Case history

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Other non-experimental methods

• Archival data
• Content analysis

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Considerations

• Reactivity of subjects
• Ethical issues
• Validity of measures

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Descriptive statistics (Ch. 11)

• Central tendency (average)
• Spread (variability)
• Shape (symmetry/skew)

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Descriptive statistics (Ch. 11)

• 82.7 60.6 74.0 93.3 97.1 81.7 86.5 40.4 76.0 83.7
  77.9 79.8 76.0 89.4 76.0 40.4 68.3 71.2 69.2 95.2
  86.5 67.3 76.0 84.6 67.3 73.1 96.2 84.6 74.0 82.7
  83.7 80.8 91.3 94.2 81.7 79.8
• need descriptions or summaries of the raw data

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Frequency distribution
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Measures of central tendency

• Mode
• Median
• Mean
• When to use each

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Measures of spread

• Range
• Interquartile range
• semi-interquartile range (Q3-Q1)/2
• Variance
• Standard deviation

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Computational formula for variance
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Advantages of Standard Deviation

• Units are the same as your measure
• Relation to normal distribution
• M1 SD represents ?68 total area
• M2 SD represents ?95 total area
• M3 SD represents ?99 total area

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Standard Scores

• Note to myself for year 2000
• Insert stuff about standard scores and Z-test
  here -- they dont get it later when talking
  about correlation

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Applicants for tutor position

• Applicant 1 Applicant 2
• Intro stats 83 73
• Advanced stats 81 68
• Intro psych 80 68
• Clinical psyc 82 78
• English comp. 83 90
• English Lit. 84 91
• Spanish 84 88
• Intermed. Spanish 86 83
• Can. Hist. 82 93
• World Hist. 85 98
• Mean 83 83

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N10 ?60 ?(XA-MA)2 80
?60 ?(XB-MB)2 48
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Shape

• Symmetrical (normal)
• Positive skew
• Negative skew
• bi (multi)-modal

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Shape
Simulations http//www.ruf.rice.edu/lane/stat_s
im/descriptive/index.html
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Descriptive stats and measurement scales

• Scale type
• Nominal
• Ordinal
• Interval
• Ratio

• Scale properties
• Differences
• Magnitudes
• Equal intervals
• True zeros

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Summarizing data

• Graphing nominal data
• Pie charts
• Bar graphs
• Frequency distributions
• Histograms
• Line graphs
• Exploratory data analysis

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Summarizing data graphically

• Visualizing your distribution
• Pie charts
• Bar charts
• Histograms
• stem and leaf plots
• box and whisker plot

• Comparing groups
• Bar graphs
• Line graphs
• box and whisker plot

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Favorite Snack Food

• Chocolate 10
• Chips 23
• Pizza 8
• Popcorn 11
• Fruit Veg 10
• Other 18

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Deceptive figures
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Age and sexual activityYoung women in Nova Scotia
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Midterm grades

• 74.0 97.1 76.9 83.7 76.9 76.9 54.8 84.6 72.1 89.4
  82.7 67.3 82.7 60.6 64.4 56.7 80.8 60.6 90.4 78.8
  84.6 72.1 76.0 89.4 41.3 83.7 68.3 84.6 90.4 84.6
  59.6 81.7 75.0 98.1 79.8 52.9 72.1 65.4 74.0 76.9
  71.2 80.8 66.3 93.3

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1st Midterm grade distribution SecA
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Midterm Box-plots
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Midterm grades

• 82.7 60.6 74.0 93.3 97.1 81.7 86.5 40.4 76.0 83.7
  77.9 79.8 76.0 89.4 76.0 40.4 68.3 71.2 69.2 95.2
  86.5 67.3 76.0 84.6 67.3 73.1 96.2 84.6 74.0 82.7
  83.7 80.8 91.3 94.2 81.7 79.8

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1st Midterm grade distribution SecB