Probability & Significance

• What is meant by the term significance?


  Tells us how sure we are about a correlation/ differnece existing
• What if a result is significant?

  We reject the null hypothesis and accept the alternative hypothesis
• What is the differnece between the null and alternative hypothesis?


  The null (H0) states there is no differnece/ correlation between the conditions. Whereas the alternative (H1) states that there is a differnece between the condititons
• What does the term 'probability' refer to?


  It is a calculation of how likely it is for an event to happen
• What does 0 probability mean?


  Statistical impossbility
• what does 1 mean in probability?


  Statistical certainty
• What is the usual level of significance in psychology?


  0.05 - the p value is usually equal to or less than 0.05 (5%)
• What does the p value being 0.05 mean? 


  The probability of the difference in the study's findings being due to chance is 5% or less - reseachers have a 95% confidence level in their results
• What if there is any risk attached to the reseach, a 'human cost' e.g. with clinical drug trials?


  The p value is set to 0.01 (1%) instead
• When a type I and type II errors made?


  when forming a conclusion from the study
• What is a type I error?


  the incorrect rejection of a null hypothesis which is actually true, so reseachers claim to have found a significant difference when there actually isn't any
• what is a type I error also known as?


  an optimistic error , false positive
• What is a type II error?


  the failure to reject the nuul hypothesis that is false, researchers claim that there is no significant difference when there actually is one
• what is a type II error also known as?


  a pessimistic error , false negative
• why do psychologists favour 5% level of significance?


  it best balances the risk of making errors