statistical testing

• researchers must find out if their findings had a significant difference. the difference found may have occurred by chance. to find this out, a statistical test must be used
• to determine whether the difference found is significant, researchers can use the sign test. to use the sign test, 1. we need to be looking for a difference rather than an association 2. we need to have used a repeated measures design 3. we need data that is organised into categories known as nominal data.
• all studies have a significance level to check for significant differences. the accepted level of probabilty is 0.05. this is the level at which the researcher decides to accept or reject the hypothesis. if the experimental hypothesis is accepted this means there is less that a 0.05 chance the findings occurred through chance.
• when the statistical test is calculated, the researcher is left with the calculated value. this needs to be compared with the critical value to decide whether the result in significant. the critical values for a sign test are given in a table of critical values. you need 1. the significance level desires (0.05) 2. the number of participants in the investigation 3. whether the hypothesis is directional or non directional. this allows the researcher to locate the critical value for the data. this critical value needs to be equal to or lower than the calculated value
• the sign test: 1. we need to convert the data to nominal data if not already by working out which participants produced a higher word count and which produced the lower word count. 2. from the table add up all the pluses and the minuses. 3. we take the less frequent sign and call the S which is our calculated value. 4. we must compare our calculated value with the critical value.
• a statistical test provides a way of determining whether hypotheses should be accepted or rejected. in psychology, the tell us whether differences or relationships between variables are statistically signifcant or have occurred by chance