Smarties Sampling

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Power point for geography fieldwork students. Provides a description of different sampling techniques using smarties (or skittles depending on your preference!)

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Smarties Sampling

  1. 1. Sampling Learning Objectives• ALL – to know differentsampling methods• MOST – reflect on advantagesand disadvantages of sampling• SOME – consider the effects ofbias
  2. 2. What I KNOW What I WOULD What I have The RANK order about sampling LIKE to know LEARNT about of what I have about sampling sampling learnt today is (the most important) Complete the first two columns of your KWL grid. Learning Objectives• ALL – to know different sampling methods• MOST – reflect on advantages and disadvantages ofsampling• SOME – consider the effects of bias
  3. 3. 1. it is quicker than measuring every item 2. it is therefore much cheaper 3. often it is impossible to measure everything The size of the sample will usually be 4. it is unnecessary to measure dictated by the time everything and resources 5. it is sometimes impossible to available. BUT the gain access to everything larger the sample Learning Objectives the more likely it is• ALL – to know different sampling methods to find a true• MOST – reflect on advantages and disadvantages of picture of the datasampling you are sampling.• SOME – consider the effects of bias
  4. 4. You will be conducting a mini investigation to practise sampling. You will be using smarties to demonstrate the different sampling techniques. Do not eat your smarties as you can’t carry out the investigation without them – make it to the end and then you can eat them!! Stretch and challenge – for each type of sampling method you must attempt to write up your own definition of this technique. Learning Objectives• ALL – to know different sampling methods• MOST – reflect on advantages and disadvantages ofsampling• SOME – consider the effects of bias
  5. 5. Random sampling means that members of a population have equal chances of being selected. To carry out this type of sampling, Lay out your smarties in a you will need to use a table of row. Assign each smartie a random numbers. Random number from 1- 20(we will numbers can also be generated deal with a population of 20 smarties). using a calculator or computer. A random number Learning Objectives calculator will generate numbers to identify which• ALL – to know different sampling methods smarties will be part of the• MOST – reflect on advantages and disadvantages of random sample.sampling• SOME – consider the effects of bias
  6. 6. Advantages Disadvantages No human bias If the sample size is small involved in the we may by bad luck selection obtain an process. unrepresentative result Learning Objectives• ALL – to know different sampling methods• MOST – reflect on advantages and disadvantages ofsampling• SOME – consider the effects of bias
  7. 7. What I KNOW What I WOULD What I have The RANK order about sampling LIKE to know LEARNT about of what I have about sampling sampling learnt today is (the most important) Add 3 things you have learnt to your table Learning Objectives• ALL – to know different sampling methods• MOST – reflect on advantages and disadvantages ofsampling• SOME – consider the effects of bias
  8. 8. Sampling data at equal distances apart e.g. every fifty meters or every 10th person. Lay out your smarties in a row. Assign each smartie a number from 1- 20(we will deal with a population of 20 smarties). Learning Objectives Take every 5th smartie• ALL – to know different sampling methods – this will be your• MOST – reflect on advantages and disadvantages ofsampling systematic sample.• SOME – consider the effects of bias
  9. 9. Advantages Disadvantages Ensures If the sample size is small complete we may by bad luck coverage of the obtain an sample area. unrepresentative result Learning Objectives• ALL – to know different sampling methods• MOST – reflect on advantages and disadvantages ofsampling• SOME – consider the effects of bias
  10. 10. Strata means All the sweets are smarties but each layer. A stratified smartie has a different colour and the sample is made up colour represents a subjection of the of different layers whole population. Select out one smartie of the population, of each colour. for example, selecting samples from different age groups. Learning Objectives• ALL – to know different sampling methods• MOST – reflect on advantages and disadvantages ofsampling• SOME – consider the effects of bias
  11. 11. Advantages Disadvantages Helps to reduce bias Sometimes difficult because all sub groups to identify a sub of the population are group or strata included in the sample Learning Objectives• ALL – to know different sampling methods• MOST – reflect on advantages and disadvantages ofsampling• SOME – consider the effects of bias
  12. 12. What I KNOW What I WOULD What I have The RANK order about sampling LIKE to know LEARNT about of what I have about sampling sampling learnt today is (the most important) Add 3 things you have learnt to your table Learning Objectives• ALL – to know different sampling methods• MOST – reflect on advantages and disadvantages ofsampling• SOME – consider the effects of bias
  13. 13. Q. Collecting sediment samples every 10m on a beach A. Systematic Q. In a beach questionnaire ensuring that participants both young and old are asked. A. Stratified Q. Numbers are generated using a computer and these numbers are used as grid reference co ordinates for the site of study A. Random Q. In a sand dune investigation choosing a sample where there is a break of slope rather than at equally spaced intervals A. Stratified Learning Objectives• ALL – to know different sampling methods• MOST – reflect on advantages and disadvantages ofsampling• SOME – consider the effects of bias
  14. 14. Select out your favourite colour smarties and eat them – this would be a bias sample! Why? Learning Objectives• ALL – to know different sampling methods• MOST – reflect on advantages and disadvantages ofsampling• SOME – consider the effects of bias
  15. 15. What I KNOW What I WOULD What I have The RANK order about sampling LIKE to know LEARNT about of what I have about sampling sampling learnt today is (the most important) Add 2-4 things you have learnt this lesson and decide which is the most important thing you have Learning Objectives learnt or rank order• ALL – to know different sampling methods everything you have learnt from top to• MOST – reflect on advantages and disadvantages of bottom.sampling• SOME – consider the effects of bias

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