Statistical testing

Question 1

What is statistical testing?

Answer 1

• it provides a way of determining whether hypotheses should be accepted or rejected
• in psychology it tells us whether differences or relationships between variables are statistically significant or have occurred by chance

Question 2

What is the sign test?

Answer 2

• a statistical test to analyse the difference in scores between related items
• data should be nominal
• in order to use the sign test:
  1. look for a difference rather than an association
  2. repeated measures design must have been used
  3. nominal data used - data organised into categories

Question 3

What is the concept of probability in statistical testing?

Answer 3

• all studies have a significance level to check for significant differences
• the accepted level of probability is 0.05 which is the level at which researcher decide to accept a hypothesis or not
• if the hypothesis is accepted there is a less than 5% probability the results are due to chance
• in some cases researchers need to be even more confident that results weren’t due to chance so have stricter significant levels like 0.01 - research may involve a human cost like drug trials where there is no possibility that it can be repeated

Question 4

What is the critical value?

Answer 4

• the number left after a statistical test has been calculated is called the calculated value
• this needs to be compared with a critical value to decide whether results are significant or not
• critical values for a sign test are given in a table
• to use the table you need:
  1. significance level desired (5% most of the time)
  2. no. of pps in the investigation (N value)
  3. whether the hypothesis is directional or non-directional
• for the sign test the calculated value has to be equal to or lower than the critical value for results to be significant