1  Introduction

1.1 Types of Variables

What are variables you would consider in buying a second hand bike?

• Brand (Trek, Raleigh)
  
• Type (road, mountain, racer)
  
• Components (Shimano, no name)
  
• Age
  
• Condition (Excellent, good, poor)
  
• Price
  
• Frame size
  
• Number of gears
  

1.2 Parametric vs Non-parametric

• Parametric stats are more powerful than non-parametric stats- for real numbers- example like t-test
  
• Non-parametric stats are not as powerful but good for category variables – example like Mann-Whitney U (Likert)
  

1.3 Types of Scales

Nominal

objects or people are categorized according to some criterion (gender, job category)

Ordinal

Categories which are ranked according to characteristics (income- low, moderate, high)

Interval

contain equal distance between units of measure- but no zero (calendar years, temperature)

Ratio

has an absolute zero and consistent intervals (distance, weight)