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Data Description

Data Description. Tables and Graphs Data Reduction. Tables and Graphs. Tables: Numerical data in a matrix format Graphs: Visual representation of data Types of Graphs/Tables: Displaying information about a single variable Frequency Cumulative Frequency

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Data Description

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  1. Data Description • Tables and Graphs • Data Reduction

  2. Tables and Graphs • Tables: Numerical data in a matrix format • Graphs: Visual representation of data • Types of Graphs/Tables: • Displaying information about a single variable • Frequency • Cumulative Frequency • Displaying information about the relationship among 2 or more variables • Scattergram • One or more IV and one or more DV • Time Series

  3. Sample of N=10 from p.418

  4. Information about a single variable: Frequency graphs and tables • Frequency Table • Counts of responses • One row for each score or range of scores • Histogram • Bar graph • Stem and leaf plot • Frequency polygon • Cumulative frequency polygon

  5. Relationships Between 2 Variables • In frequency plots, x axis is DV, but in most plots with 2 variables, DV is on y axis • Scattergrams • Tables with 1 IV and 1 DV (2 variables) • Tables with more than 1 IV (more than 2 variables) • Line and Bar Graphs • Time Series Graphs

  6. Scattergrams • Used to show correlations • Any type of variable (IV or DV) can be on either axis, but often have DV on ordinate and IV on abscissa • Each plotted point represents the score of one individual on two separate variables

  7. Tables with 2 or more Variables • In a table, the scores represent the DV • The columns represent the levels of the IV • With only 1 IV, there will be only 1 row • With 2 IVs, the rows will represent levels of the second IV • Additional IVs will be represented as groups of columns

  8. Graphs with 2 or More Variables • DV is represented on the y axis • Levels of IV or IVs are represented on the x axis • With 2 or more IVs, levels of an IV may be represented by color, shape, or shading • Bar graphs are appropriate for categorical IVs • Line graphs are appropriate only for quantitative IVs on x axis

  9. Time Series Graphs • X axis represents passage of time

  10. Data Reduction • Prepare the data sheets for transferring data • Transcribe data onto a data summary sheet • Matrix containing all the data • One data point per row • Columns represent variables (DV in last column usually) • Create coding guide • Use coding guide to create computer data file • Check for missing data, invalid data, and outliers (descriptive statistics, or exploratory data analysis) • Proceed with analysis (descriptive and inferential statistics)

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