Statistical Tests (- sign) Flashcards
When is Spearman’s rho used?
When a relationship (correlation) is predicted between two sets of data, the data is at least ordinal and the data are pairs of scores from a repeated measures or match pairs design
Why would data come in pairs (Spearman’s)?
Either because the same participant took part in both conditions (repeated measures) or because the participants are matched up (matched pairs)
What is Spearman’s rho also used to create?
Correlational coefficients which tells the researcher about the strength and direction of a correlation
What are all Spearman’s rho scores between and what do the scores mean?
All between -1 and 1
If Spearman’s rho is negative that means a negative correlation, if its positive it means a positive correlation
The closer to -1 and 1 the Spearman’s rho is, the stronger the correlation
How does a Spearman’s rho test work?
The test gives an observed value (called rs)
Once you’ve got rs, look at the critical values table to see if the results are significant
You need to know the sample size (N) for this
What is Pearson’s r test?
A parametric test used when a relationship (correlation) is predicted between two sets of data, the data is normally distributed, the data is interval/radio data and the data are in pairs of scores from repeated measures or matched pairs design
When would Pearson’s r test be used?
When data comes in pairs (repeated measures or matched pairs)
Data is interval//ratio level
What are Pearson’s r test also used to create?
Correlational coefficients which tells the researcher about the strength and direction of a correlation
What are Pearson’s r scores always between and what do they mean?
All between -1 and 1
If Spearman’s rho is negative that means a negative correlation, if its positive it means a positive correlation
The closer to -1 and 1 the Spearman’s rho is, the stronger the correlation
How does the Pearson’s r test work and what do you need to know?
The test gives you an observed value (called r)
Once you’ve got r, look at the critical values table to see if the result is significant
You need to know the degree of freedom for looking at the table which is calculated N(sample) - 2
In both Spearman’s rho and Pearson’s r what must the calculated value of either rs or r be in order for significance to be shown?
Equal to or greater than the critical value in the table
What is the Wilcoxon test?
Also known as the Wilcoxon signed-matched ranks. It is used when a difference is predicted to occur between two sets of data, the data is normally distributed, the data is of at least ordinal level and a related measure has been used
When do psychologists use the Wilcoxon test?
The data come in pairs (repeated measures or matched pairs)
The data from two different conditions can be put in order of size
How does the Wilcoxon test work and what do you need to know?
Gives you an observed value, called T
Once you have T, look at the critical values table to see if the results are significant
Need to know the sample size (N - for the Wilcoxon test), you only use pairs of scores that are different
What must the value of T be in the Wilcoxon test to shown significance?
Equal or less than the critical value - if it is, the result is significant and the null hypothesis can be rejected
What is the Mann-Whitney test?
Used when a difference is predicted between two sets of data, the data is of at least ordinal level and an independent group design has been used
When would psychologists use a Mann-Whitney test?
There is only one result for each participant - no participant appears in the results for both groups (independent group)
Data from the two different conditions can be put into order of size
How does the Mann-Whitney test work?
Gives two observed values called U1 and U2- (one for each of samples)
Once you have both U values, the lowest one becomes the U value and is used to see if the results are significant
Why are their two tables in the Mann-Whitney test?
One for one-tailed hypothesises and one for two-tailed hypothesises
First table= critical values of U for the one tailed Mann-Whitney test at p=0.05 or the two-tailed at p=0.10
Second table = critical values of U for the two/one?-tailed test at p=0.25 or the two tailed at p= 0.05
How is significance decided in the Mann-Whitney test?
If U is equal to or less than the critical value, the result is significant and the null hypothesis can be rejected
What is the related t-test?
Also called the dependent t-test
parametric test that is used when a difference is predicted between two sets of interval/ratio data and the data is gathered using repeated measures or matched pairs
When do psychologists use the related t-test?
The data comes from research that uses the repeated measures or matched pairs design
The data is normally distributed and is interval data
How does the related t-test work and what do you need to know
It gives you an observed value called t
Once you have t, look at the critical values tables to see if the results are significant
For this, need to work out the degrees of freedom to help find the critical value
How do you work out the degrees of freedom (Df) (related t-test)?
N (number in sample) - 1
How is significance determined in the related t-test?
Calculated value of t must be equal to or greater than the critical value for significance to be shown
What is the unrelated t-test?
Also called the independent t-test
A parametric test that is used when a difference is predicted between two sets of interval/radio data and the data is gathered using independent groups design.
How does the unrelated t-test work and what will you need?
The test gives an observed value called t
Once you have t, look at the critical values table to see if the results are significant
Need to work out the degrees of freedom to help find the critical value
How do you work out degrees of freedom for the unrelated t-test?
Nx (number of RPS in the 1st sample) + Ny(Number of RPS in the 2nd sample) - 2
In the unrelated t-test, what happens if the t is a negative number?
The negative sign is ignored
How is significance determined in the unrelated t-test?
Calculated value of t must be equal to or greater than the critical value for significance to be shown
What is the chi-squared test?
Used when a difference is predicted between two sets of data. The data is at least nominal and an independent group design has been used. It’s possible to use chi-squared with correlations as a test of association
When do psychologists use the chi-squared test?
The data is about frequencies for different categories (this is nominal data and it is best if these categories don’t have a particular order like size)
The data is from Independent group design, meaning each RPS only appears once in the results
How does the Chi-squared test work and what will you need to know?
Gives an observed value called X2
Once you’ve got this, look at the critical values table to see if the results are significant
Will need to know what the degrees of freedom are
In the chi-squared test how are the degrees of freedom worked out?
(Number of rows -1) x (Number of columns -1)
How is significance determined in the Chi-squared test?
Calculated value of X2 must be equal to or greater than the critical value for significance to be shown
