Chapter 1: Data collection

• Population


  All the items of interest
• Census


  Involves measuring all of the population
• Sampling units


  Individual units of the population
• Sampling frame


  An individually numbered list of all the sampling units
• Sample


  A subset of the population
• Simple random sampling

  Use a sampling frame to assign each item a number and randomly select numbers - this is a random sampling method
• Systematic sampling

  Take items from a list at regular intervals. This is a random sampling method
• Stratified sampling

  Use simple random sampling to select items proportionally from mutually exclusive strata. This is a random sampling method
• Quota sampling

  Select a sample using a non random method until you have data which represents differing characteristics of the population. This a non random sampling method
• Opportunity sampling

  Taking a sample based on what is available at the time. This is a non random sampling method
• Quantitative data

  Numerical data
• Qualitative data

  Non numerical data
• Discrete variables

  Variables that can take certain values
• Continuous variables 


  Variables that can take any value
• LDS - DMT

  daily mean temperature, measured in degrees C
• LDS - DTR

  daily total rainfall, includes snow or hail, less than 0.05mm is recorded as 'tr' or 'trace'
• LDS - DTS

  daily total sunshine, recorded to the nearest 10th of an hour
• LDS - DMWD

  daily mean wind direction, recorded as a bearing and a compass direction
• LDS - DMWS

  daily mean wind speed, recorded in knots, 1 knot = 1.15mph
• Beaufort scale

  (number = description)

  • 0 = calm
  • 1-3 = light
  • 4 = moderate
  • 5 = fresh
• LDS - DMG

  daily maximum gust, recorded in knots with a direction
• LDS - DMRH

  daily maximum relative humidity, recorded in % air saturation with water, 95%+ shows mist or fog
• LDS - DMCC

  daily mean cloud cover, recorded in octas which is the number of eights of the sky covered in cloud
• LDS - DMV

  daily mean visibility, recorded in decametres, 1 decametre = 10m, it is the greatest horizontal distance that can be seen in daylight
• LDS - DMP

  daily mean pressure, recorded in hectopascals (hPa)
• LDS - Camborne

  Cornwall, England
• LDS - Heathrow

  London, England
• LDS - Hurn

  Dorset, England
• LDS - Leeming

  Yorkshire, England
• LDS - Leuchars

  East Scotland
• LDS - Beijing

  China, Northern Hemisphere
• LDS - Jacksonville

  Florida, USA
• LDS - Perth

  South west Australia
• List the LDS locations

  • LOCATIONS:
  • perth
  • jacksonville
  • beijing
  • leuchars
  • leeming
  • hurn
  • heathrow
  • camborne