Data Collection

• Population: Whole set of items in interest
• Sample: A subset of the population intended to represent the population
• Sampling Unit: Anything that can be sampled
• Sampling frame: A list of sampling units
• A population is general and a sampling frame is specific
• Samples are drawn from a sampling frame
• Data collected from the population is known as a census
• Census Advantages

  • Accurate
• Census Disadvantages

  • Time consuming
  • Expensive
  • Can't represent small samples
• Sample Advantages:

  • Cheap
  • Quick
  • Less Data
• Sample Disadvantages

  • Less Accurate
  • Not externally used
• Simple Random Sampling: A sampling technique that involves selecting a sample from a population by randomly selecting a sample of individuals from the population
• Systematic Sampling: A sampling technique that involves selecting a sample from a list of numbers that are in order of size
• Stratified Sampling: Population are divided into groups and then a random sample is carried out per group, this is used in a large population
• Quota Sampling: Divide population to characteristic then select the relevant group for the sampling
• Opportunity Sampling: Taken from avaliability
• Advantages of Simple Random Sampling:

  • No bias
  • Easy
  • Cheap
• Advantages of Systematic Sampling:

  • Easy
  • Quick
  • Suitable
  • For large populations
• Advantages of Stratified Sampling:

  • Reflects population structure
  • Guarantees proportional research
• Advantages of Quota Sampling:

  • Flexible
  • No sampling frame required
  • Quick
  • Easy
  • Comparable
• Advantages of Opportunity Sampling:

  • Easy
  • Cheap
• Disadvantages of Simple Random Sampling:

  • Unsuitable for large populations
  • Sampling frame needed
• Disadvantages of Systematic Sampling:

  • Sampling frame needed
  • Can be bias if the frame isn't random
• Disadvantages of Stratified Sampling:

  • Population must be clearly classified
  • Sampling frame needed
• Disadvantages of Quota Sampling:

  • Can introduce bias
  • Potentially inaccurate
  • Scope can increase groups which becomes time consuming
  • Non-responses aren't recorded
• Disadvantages of Opportunity Sampling:

  • Low external validity
  • Highly dependent on individual researcher
• Types of Data

  • Qualitative
  • Quantitative
• Types of Quantitative Data

  • Discrete
  • Continuous
• Discrete Quantitative Data: Data that can be counted and expressed as a whole number
• Continuous Quantitative Data: Data that can be measured on a scale and can take any value between two extremes
• Identify

  A) lower bound

  B) upper bound

  C) class width