Statistics Chapter 1: Collecting Data

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  • Statistics Chapter 1: Collecting Data
    • Census v Sample
      • Sample = Part of Population
        • Two Types
          • Random
            • Simple Random
            • Stratified (number in strata/total*sample size)
            • Random number generator
          • Non Random
            • Quota Sampling - Se number (20 teenage boys etc)
            • Cluster - Data Split into clusters, pick one randomly
            • Systematic - Number in sample/total=collect every....values from random starting point
        • Sampling Frame = List of all people/items in Sample
          • Sampling Unit = All people/items in sample
      • Census=Whole Population
      • Census Ads: Unbiased/Accurate/Fully Representative
        • Disads: Difficult to use whole population/expensive/time consuming
      • Sample Ads: Less time consuming/Cheap/no need to collect lots of data
        • Disads: May Be biased/unrepresentative
    • Primary v Secondary Data
      • Primary Ads: Accuracy known/know how obtained
        • Primary Disads: Time consuming/Expensive
      • Secondary Ads: Easy/cheap to obtain
        • Disads: May be out of data/May contain Mistakes/Method of collection unknown
    • Capture Recapture
      • N=(Mn)/(m)
      • Assumptions: No births or deaths/No migration (same subjects)/marking doesn't affect
    • Pilot Surveys/Control Groups
      • Pilot Survey: Small version of sample to see if qs are right and see results
      • Control Group: Used in Drug Trials placebo/two groups etc
      • Questionnaires
        • Closed Question: Specific Answers but may not cover all
        • Open Questions: Any answer but may not get answer needed
        • Leading Questions = Bad
    • Quantitative/Qualitative
      • Continuous/Discrete
        • Categorical - Sorted into non overlapping categories
          • Ranked - Can be put in order
            • Bivariate - Pairs of related variables


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