Types of data

• Primary data


  Data that has been obtained first hand by the researcher directly from the participants in the research through the use of an experiment, self-report or observation
• Strengths of primary data

  • Data will match the research aim as the person designed their own investigation, increasing validity
• Weaknesses of primary data

  • Time and effort required, may not give an overview of an area
• Secondary data


  Data that has been collected by someone else and pre-dates the current research
• Strengths of secondary data

  • Quick, cheap and easy, gives a good overview with large sample sizes (meta-analysis)
• Weaknesses of secondary data

  • Data will not match the research aim as the person has not designed their own investigation
• Quantitative data


  Numerical data
• Strengths of quantitative data

  • Easier to analyse and draw conclusions
• Weaknesses of quantitative data

  • Oversimplifies reality
• Qualitative data


  Non-numerical descriptive data
• Strengths of qualitative data


  • Provides rich detail
• Weaknesses of qualitative data

  • Analysis relies on interpretation by the researcher- subjective, not easy to categorise/analyse
• Measures of central tendency

  • Mean
  • Median
  • Mode
• Mean


  Calculated by adding up all of the scores and dividing by the number of scores
• Advantages of the mean

  • The mean can be said to be representative of all of the data collected as it is calculated using all the individual values
• Disadvantages of the mean

  • It can be misrepresentative of the numbers if there is an extreme value
• Median


  The middle value of an ordered list
• Advantages of the median

  • It is not affected by extreme scores
• Disadvantages of the median

  • Only reflects one value therefore is not as sensitive as the mean
• Mode


  The value that is most common
• Advantages of the mode

  • It is useful when the data is in categories (e.g. the number of people who like marshmallows)
• Disadvantages of the mode

  • Not useful when there are several modes or when the mode is numerically further from the middle
• Measures of dispersion


  • Range
  • Standard deviation
• Range


  The difference between the highest and lowest numbers
• Standard deviation


  A more precise measure of the spread of data as it is not distorted by a single extreme score, taking into account how spread out all of the values are from the mean
• Relationship between standard deviation and data spread

  • The higher the standard deviation, the more the data is spread out around the mean