1. DATA TABLES Kinds of variables… DISPLAYING ONE CATEGORICAL VARIABLE Frequency tables…Bar charts…Pie charts… EQUAL AREA PRINCIPLE COMPARING TWO VARIABLES Paired vs. Unpaired data

2. DATA TABLE classsiblingsmilessalarysinger 2008111800004.5 20113180350003 360003 20110400400004 2010220400000 Columns = Variables Rows =Individuals =Cases =Subjects =Records Unique key? Do the rows have any particular sequence? Missing Data

3. Kinds of Variables CATEGORICAL --- nominal --- values are just labels ordinal --- values are just labels, but have a sequence QUANTITATIVE --- discrete --- only certain (separated) values are possible continuous --- all values are possible in some range

4. Frequency table - sex VALUECOUNT Female46 Male26 TOTAL72

5. Frequency table - sex VALUECOUNTPERCENT (of column) Female4664% Male2636% TOTAL72100%

6. Frequency table - singing VALUECOUNTPERCENT 11521% 22129% 31926% 41521% 53 4% TOTAL73100%

9. EQUAL-AREA PRINCIPLE Areas are in proportion to data values.

10. Comparing two variables UNPAIRED DATA: Variables from different data tables, referring to different groups of individuals  This year’s “singing” variable vs. last year’s “singing” variable  Experimental hamsters vs. control-group hamsters PAIRED DATA: Variables from same data table  “Singing” variable vs. “Siblings” variable  “Before” vs. “After” for same hamsters

11. Summary…Key ideas DATA TABLES Individuals, Variables… TYPES OF DATA Categorical (Nominal, Ordinal), Quantitative… Paired vs. unpaired variables FREQUENCY TABLE BAR CHART Equal area principle… PIE CHART