Inferential testing

• Choosing a statistical test

  Simon Cowell wants more singers receiving unanimous praise

  Sign Test

  Chi-squared

  Wilcoxon

  Mann-whitney u

  Spearman's Rho

  Related t-test

  Unrelated t-test

  Pearson's r
• Nominal Data


  Data of categories only. Data cannot be arranged in an ordering scheme. (Gender, Race, Religion)
• ordinal data


  data exists in categories that are ordered but differences cannot be determined or they are meaningless. (Example: 1st, 2nd, 3rd)
• Interval Data


  Interval data are based on numeric scales in which we know the order and the exact difference between the values. Using units of measures such as cm, g
• Probability


  A measure of likelihood that a particular event will occur where 0 indicates statistical impossibility and 1 statistical certainty.
• Significance


  A statistical term that tells us how sure we are that a difference or correlation exists. A 'significant' result means that the researcher can reject the null hypothesis.
• Critical value


  when testing a hypothesis, the numerical boundary or cut-off point between acceptance and rejection of the null hypothesis
• Type 1 error (false positive)

  The incorrect rejection of a true null hypothesis
• Type 11 Error (False Negative)

  The failure to reject a false null hypothesis
• level of significance


  The usual level of significance is 0.05 (5%) or in a medical study it is 0.01 (1%). This means that the probability that the observed effect was down to chance is 5%.