Statistical Testing

• Concept of significance

  Statistical testing is used to find out if the difference we found between dependent variable was by chance: coincidence or fluke.
• Sign Test

  To determine whether the difference we found is significant, we can use simple statistical calculations like the sign test.
• 3 Important things for the sign test

  We need to look for a difference and not an association, a repeated measures design, nominal data
• Concept of probability

  All studies employs a significance level to check for a significant difference/relationship. Accepted level of probability in psychology is 0.05 (5%), which is the level where the researcher decides to accept the hypthesis or not.
• Acceptance of hypothesis

  If the hypothesis is accepted, there is less than 5% probability that the results occurred by chance. Researcher therefore can be sure the independent varibable manipulation caused a difference.
• Level of probabiltity in more severe circumstances


  When the cost of human life is involved, researchers need to have a more critical/stricter significance level of 00.1 (1%). This may be used in situations where new drugs are being tested.
• Calculated value

  The number the researcher is left with after the statistical test has been calculated. It is compared to the critical value to see whether the results are significant.
• Table of values

  Critical values given for a sign test in a table of critical values. On the table, the significance level desired is presented (5%), the number of ppts and whether the hypothesis is directional/non-directional