Data Description

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 N10 from p.418
ID Sex A (weight) F (recall) G (correct)
04 m 3 10 11
60 f 6 14 14
35 f 3 12 6
33 f 5 12 11
31 m 2 13 15
20 m 5 12 12
55 m 4 12 11
57 m 6 11 11
34 f 4 13 12
21 m 5 12 12
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)