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Policy Research 101 Statistical Basics & How to Read Research Reports

Policy Research 101 Statistical Basics & How to Read Research Reports. Keith Curry Lance Consultant RSL Research Group. Qualitative data Observational notes Interview transcripts Documents, images Video, audio Quantitative data Nominal Ordinal Interval/ratio. Data collection

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Policy Research 101 Statistical Basics & How to Read Research Reports

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  1. Policy Research 101Statistical Basics &How to Read Research Reports Keith Curry Lance Consultant RSL Research Group

  2. Qualitative data Observational notes Interview transcripts Documents, images Video, audio Quantitative data Nominal Ordinal Interval/ratio Data collection Available data Survey Focus group/key informant interview Other Types of Data & Data Collection

  3. Quantitative Data • Nominal (different groups) • Gender, racial/ethnic groups • Administrators, teachers, students • Ordinal (more/less groups) • Age groups • Educational attainment levels • Strongly agree to disagree scales • Interval/Ratio (zero, equal intervals) • Numbers (1-N), percentages

  4. Data Quality Criteria • Currency (i.e., time period covered by data) • Timeliness (i.e., how quickly after that time period data are reported) • Completeness • Validity (i.e., meaningfulness) • Reliability (i.e., repeatability)

  5. Description vs. Analysis • Describing what is • Analyzing cause and effect

  6. Descriptive Statistics • Frequencies, percentages • Means, medians • Quartiles, percentiles • Comparisons, rankings • Trends

  7. Frequencies & Percentages

  8. Mean Arithmetic average More sensitive to extreme cases Better suited to interval/ratio data (i.e., with zero) Example: population of legal service area Median 50th percentile (middle value) Less sensitive to extreme cases Better suited to ordinal data (i.e., no zero) With even N of cases, median = mean of middle two Means & Medians

  9. Quartiles 1st, 25th %ile 2nd, 50th (median) 3rd, 75th %ile Interquartile range (1st-3rd quartiles—boundaries of middle half) Example: ALA Salary Survey Percentiles In practice, usually deciles 10th, 20th, 30th, etc Example: old standardized test scores Quartiles & Percentiles

  10. Analytical Statistics • Cross-tabulation • Comparison-of-means • Correlation

  11. Analytical Statistics • Cross-tabulation • Two nominal variables • Materials format and circ status (circulated in past year)

  12. Analytical Statistics • Comparison-of-means • One nominal, one ordinal or interval • % of students using databases for public libraries with and without remote access

  13. Analytical Statistics • Correlation • Two interval level variables • HPW of school librarian staffing and test scores • School poverty status and test scores • Perfect correlation (i.e., any variable with itself) = 1.00

  14. How to Read Research Reports • What is the issue at hand? • What type of data is presented? • How was data collected? • Is data descriptive or analytical? • What do I know about its quality? • What does it tell me? • What do I still not know?

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