Inferential testing

• Inferential statistics use collected data from the sample to make interferences (assumptions) about the behaviour of the entire target population.
• Descriptive statistics are measures of central tendency and measures of dispersion, summarising and describing raw data researchers have collected to make their sample.
• Probability is where researchers test the collected data to assess the probability of the results occurring due to chance. If they are due to chance (p=<0.05) then the results are judged to be significant and the alternative hypothesis is accepted.
• Statistical tests are mathematical tools used by researchers to determine if the results are significant.
• Find the critical value from a table:

  1. Identify the number of participants (N) or degrees of freedom (df) in the study. This is usually given in the stem.
  2. Identify the level of significance. Usually this is 0.05, but 0.01 can be used if the study is a replication.
  3. Identify if it is a directional or non-directional test.
• df = (r-1) x (c-1)

  r = number of rows,

  c = number of columns.
• The sign test:

  1. Subtract each participants score in condition B from A and state whether it is positive or negative.
  2. Work out the number of participants, excluding any who have the same score in both conditions.
  3. Work out (S), the least frequent sign. This is the calculated value.
  4. Find the critical value using the table and read across from N.
  5. Compare the critical value to S and state if significance is shown.