Research Methods Y1 - Spearman's and Pearson's Flashcards
What is the purpose of Spearman’s rho?
Spearman’s rho is a test of correlation between two sets of values. It is selected when one or both variables are ordinal level. It investigates a correlation rather than a difference.
What are the hypotheses in the Spearman’s rho example?
Alternative hypothesis: There is a positive correlation between ratings of physical attractiveness given to two partners in a relationship. (directional, one-tailed).
Null hypothesis: There is no correlation between ratings of physical attractiveness given to two partners in a relationship.
What is the first step in Spearman’s rho?
Rank each set of scores separately in each group or condition. If two or more scores share the same rank, find the mean of all tied ranks.
How is the difference calculated in Spearman’s rho?
Find the difference between each pair of ranks and square the difference for each pair. Then sum up the squared differences (Σ𝑑^2).
How is the value of rho calculated in Spearman’s rho?
rho = 1- 6(sum of d^2)/N(N^2 - 1)
What is the critical value in Spearman’s rho?
The critical value depends on the level of significance (e.g., 0.05) and whether the test is one-tailed or two-tailed. It is found in the critical values table for Spearman’s rho.
How do you determine significance in Spearman’s rho?
If the calculated value of rho is more extreme than the critical value, the null hypothesis is rejected, and the alternative hypothesis is accepted.
What is the purpose of Pearson’s r?
Pearson’s r is a test of correlation between two sets of values. It is used when data are interval level and investigates a correlation rather than a difference.
What are the hypotheses in the Pearson’s r example?
Alternative hypothesis: There is a positive correlation between the number of days participants have been using biofeedback and the reduction in their resting heart rate. (directional, one-tailed).
Null hypothesis: There is no correlation between the number of days participants have been using biofeedback and the reduction in their resting heart rate.
How is the difference calculated in Spearman’s rho?
Calculate sum of scores for x and y.
Square each x and y value
Multiply x and y for each pp and then add these xy together
How is the value of r calculated in Pearson’s r?
r = N(sum of xy) - (sumofx)(sumofy)/square root of (Nxsumof x^2 - (sumofx)^2) x (N x sum of y^2 - (sum of y)^2)
What is the critical value in Pearson’s r?
The critical value depends on the level of significance (e.g., 0.05), the number of pairs (
𝑁
N), and whether the test is one-tailed or two-tailed. It is found in the critical values table for Pearson’s r.
How do you determine significance in Pearson’s r?
If the calculated value of
r is greater than the critical value, the null hypothesis is rejected, and the alternative hypothesis is accepted.
What is a ‘Correlation test’?
A correlation test examines the strength and direction of a relationship between two variables.
What does ‘Ordinal-level data’ mean?
Ordinal-level data refers to data that can be ranked or ordered but does not have equal intervals between values.
