stats year 1

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  • Y1 STATS
    • population - whole set of all the individuals
      • census - measures every member of the population
        • advantages - gives accurate result
        • disadvantage- time consuming and expensive, cannot be used if the process destroys the item
      • sample - a small portion of the population
        • advantages - less time consuming/expensive, fewer people, less data to process
        • disadvantage- not as accurate, sample might not be big enough to give info about small sub-groups of the population
      • sampling units - individual units of population.     sampling frame - individually numbered or name e.g. list
    • random sampling
      • simple random sampling - completely random, every sample has an equal chance
        • advantages - free of bias, easy and cheap
        • disadvantage- not suitable when large population, sampling frame needed
      • systematic - required elements chosen at regular intervals
        • advantages - simple, quick, good for large populations
        • disadvantage - sampling frame needed, introduce bias if sampling frame is not random
      • stratified - population divided into mutually exclusive strata and random sample taken from each
        • advantages - accurately reflects the population structure, gives proportional representation of groups within a population
        • disadvantage - population must be clearly classified into distinct strata
    • non random sampling
      • quota sampling - select sample that reflects whole population
        • advantages - allows a small sample to be representative of the whole population, no sampling frame needed
        • disadvantage - can introduce bias, population must be divided into groups = costly
      • opportunity - sample of people available at time
        • advantages - easy to carry out, inexpensive
        • disadvantage - unlikely to be representative, dependent on researcher


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