Statistics Flashcards

• Primary Data


  Data collected by, or for, the person using it
• Secondary Data


  Data that has already been collected by someone else
• Advantages of Primary Data


  • Accurate
  • Collection method known
  • Can find answers to specific questions
• Disadvantages of Primary Data


  • Time consuming
  • Expensive
• Advantages of Secondary Data


  • Cheap
  • Easy
  • Quick
  • Data from some organisations can be more reliable than data collected yourself
• Disadvantages of Secondary Data


  • Method of collection unknown
  • Data may be out of date
  • May contain mistakes
  • May come from unreliable source
  • May be difficult to find answers to specific questions
• Types of Data


  • Quantitative - numerical observations or measurements
  • Qualitative - non-numerical observations
  • Continuous - can take any value on a continuous numerical scale
  • Discrete - can only take particular values
  • Categorical - can be sorted into non-overlapping categories
  • Ordinal - can be written in order of be given a rating scale
  • Bivariate - involves a pair of related data
  • Multivariate - involves sets of 3 or more related data values
• Population


  Everything or everybody that could possibly be involved in an investigation
• Census


  A survey of a whole population
• Sample


  A smaller number of items from the population
• Biased Sample


  Not representative of everyone in the population
• Sampling frame


  A list of people/items that are to be sampled
• Features of a good questionnaire


  • Short questions
  • Simple language
  • No leading questions
  • Non-overlapping boxes
  • Time frame in question
  • Option boxes are exhaustive
  • No personal questions
• Open question


  Has no suggested answers
• Closed question


  Has a set of given answers to choose from
• Pilot survey


  A small scale version of the survey to test the design and methods of that survey
• Hypothesis


  A statement made as a starting point of an investigation
• Cleaned data


  Made by identifying and assessing extreme values, missing data and errors before it is used
• Extraneous variables


  Variables you are not interested in but could affect the result of your experiment
• Control group


  Used to test the effectiveness of a treatment
• Using a control group


  1. Use random selection to select 2 groups of people

  2. Give the test group the treatment, control group no treatment

  3. Compare results from 2 groups to see how effective treatment is
• Matched Pairs Test


  2 groups of equally matched (age/gender etc.) people used to test effect of a particular factor. Everything in common except factor being studied
• Simulations


  Model random real life events, to help you predict what could actually happen. May be easier and cheaper than collecting real life data
• Petersen Capture-Recapture Formula


  Used to estimate population size
• Random Response Method


  Uses a random event to decide how to answer a question
• Assumptions for Petersen Capture-Recapture Formula


  • Population has not changed - no births/deaths
  • Probability of being caught is equally likely for all individuals
  • Marks/tags not lost
  • Sample size is large enough
• Random Sampling


  Every member of the population has an equal chance of being selected
• Advantages of Random Sampling


  • Sample is more likely to be representative of the population, provided it is large
  • Choice of members of sample is unbiased
• Disadvantages of Random Sampling


  • Needs a full list of the whole population
  • Needs a large sample size
  • Can be expensive and time consuming
• Types of Data


  • Discrete Data - raw value, grouped data with no inequalities, cumulative frequency step polygons
  • Continuous data - grouped data with inequalities, cumulative frequency curves, histograms
• Systematic Sampling


  Choose a starting point from the sampling frame at random, and then choose items at regular intervals
• Types of Experiments


  • Laboratory Experiments - conducted in a controlled environment
  • Field Experiments - carried out in test subjects' everyday environment
  • Natural Experiments - carried out in test subjects' everyday environment but researcher has no control over any variables
• Explanatory Variable


  The variable the researcher changes to see the effect on the response variable
• Response Variable


  The variable the researcher measures to see the effect of changing the explanatory variable
• Advantages of Laboratory Experiments


  • Easy to replicate because you can copy the experiment exactly
  • Extraneous variables can be controlled
• Disadvantages of Laboratory Experiments


  • Test subjects may behave differently under test conditions than in real life
• Advantages of Field Experiments


  • More likely to reflect real life behaviour
• Disadvantages of Field Experiments


  • Cannot control extraneous variables
  • Difficult to replicate exactly
• Stratified Sampling


  Members of each stratum (group) are in proportion to the size of the stratum. Sample from each strata is selected using random sampling
• Stratified Sampling


  Number selected from strata = (total population × strata size) / sample size