Data

Data

1. Types of Data

   • Primary vs Secondary
     • Primary: We directly observe it
     • Secondary: We do not directly observe it
   • Population vs Sample
     • Population: All members of a specified group
       • Parameter: A descriptive measure of a population
     • Sample: A subset of a population
       • Sample Statistic: A value derived from or descriptive of a sample
         • Sampling error
           • The difference between the observed sample statistic and the value for the population
       • Methods of Sampling
         • Random
           • Each occurrence within the population has an equal chance of being selected
         • Non-Random
           • Stratified Random Sample
             • Population is divided into strata, each stratum then has a proportional sample taken from it
           • Quota Sampling
   • Time Series vs Cross Sectional
     • TS: Data taken over a time period
     • CS: Data taken across a population

2. Nature of Data

   • Categorical
     • Data can be split into mutually exclusive groups
     • Avoid using descriptive stats with this kind of data unless they are specifically order stats e.g. mean
   • Ordinal
     • Data that is ordered logically, e.g. rating a consumer's experience on a scale of 1-3
     • Generally cannot use descriptive stats with this kind of data

3. Data Distribution

   • Continuous Variable
     • Data can take on any value within a range, therefore the frequency of each outcome is effectively uncountable.
     • E.g. Amount of rainfall in August
   • Discrete Variable
     • Data can take on a countable number of outcomes, therefore the frequency of each outcome can be measured.
     • E.g. Number of rainy days in August