inferential tests Flashcards
When is the sign test used?
This test is used when investigating a difference, using a repeated measures design, and the data are nominal (arranged into categories).
For example, a researcher investigated whether listening to music hinders the ability to solve puzzles. The participants had to complete a puzzle in silence, and a different one when listening to music. The time taken to solve the puzzles was calculated in each case. The hypothesis was that ‘participants will take longer to complete a puzzle when listening to music than they will to complete a puzzle in silence’.
What must the observed value be if the statistical test has an ‘r’ in the name?
If the statistical test has an ‘r’ in the name, the observed value must be equal to or greater than the critical value for significance to be shown. If not, the observed value must be equal to or less than the critical value for significance to be shown.
What must a researcher know to calculate the critical value?
Whether a one-tailed (directional) or two-tailed (non-directional) hypothesis is being used
The number of participants in the study (N)- for some tests ‘degrees of freedom’ (df) are used instead
The level of significance- which will be (unless stated otherwise) 0.05 or 5%.
What is a type I error?
Type I error:
the alternative/experimental hypothesis is mistakenly accepted, so the null is mistakenly rejected. Therefore, the researcher says that there is a significant difference between the groups, but in reality there isn’t (the null hypothesis should have been accepted).
What is a type II error?
Type II error:
the null hypothesis is mistakenly accepted, so the alternative/experimental is mistakenly rejected. Therefore, the researcher says that there is not a significant difference between the groups, but in reality there is (the alternative hypothesis should have been accepted).
When is a Mann-Whitney test used?
Used when looking for a difference, using an independent groups design, and the data is ordinal.
What is ordinal data?
Ordinal level data is data that is presented in rank order (e.g. places in a beauty contest, or ratings for attractiveness).
What is nominal data?
Nominal level data is frequency data that consists of the number of participants falling into categories. (e.g. 7 people passed their driving test the first time and 6 people didn’t)
