Operationalising Research

Inferential Statistics

• Only random sampling entitles the use of inferential statistics
  
  
• Below is the result of an imaginary survey in which a random sample of an adult population were asked whether or not they smoked.
  
  

• • Null hypothesis: there is no difference in the population between the proportions of men and women who smoke
    
    
  • The table suggests that 54% of the men and 53% of the women are smokers
    
    
  • This might be taken to indicate that men are (slightly) more likely than women to be smokers
    
    
• Question
  
  
  • How likely is it that a difference of this magnitude will arise purely as a result of random error?
    
    
• If the probability of obtaining a difference of this magnitude is less than 0.05 (1 in 20) then, conventionally, we can claim that the results are statistically significant
  
  
• Questions
  
  
  • Does it matter whether the sample of 3112 people are drawn from the population of the UK (approx. 55 million) or from The People's Republic of China (approx. 1300 million)?
    
    
  • If we multiply all of the numbers by 10 (eg imagine we had taken a random sample of size 31, 120), is the answer to the previous question the same?
    

to: Luria