OCR A-Level Psychology H567
Research Methods and Techniques
Planning and Conducting Research
Data Recording, Analysis and Presentation
Report Writing and Scientific Communication
Practical Activities and the Nature of Science
Mathematical Requirements for Research Methods
Studying and Evaluating the Core Studies: The Common Framework
Core Studies: Social Area
Core Studies: Cognitive Area
Core Studies: Developmental Area
Core Studies: Biological Area
Core Studies: Individual Differences Area
Areas and Perspectives in Psychology
Debates in Psychology
Practical Applications of Psychology
Issues in Mental Health
Child PsychologyApplied option
Criminal PsychologyApplied option
Environmental PsychologyApplied option
Sport and Exercise PsychologyApplied option
Methodological Issues and Debates Running Through Applied Psychology
Mathematical Requirements for Research Methods
Solving equations for Spearman's rho and chi-square
- 3 things to know
- Component 01
Overview
Recall questions on calculating Spearman's rho, interpreting rho values, the chi-square formula, calculating and using degrees of freedom, and why N and units must be substituted correctly into formulae.
What you need to know
Answer each one before you reveal it.
Why should a calculated value of rₛ never be greater than 1?
How are the degrees of freedom for a chi-square test calculated?
Questions from this subtopic
Each one with the model answer underneath.
- 1
In a Spearman's rho calculation N is 10 and Σd² is 33. Calculate rₛ.
Model answer
The numerator 6 × 33 is 198 and the denominator 10 × 99 is 990, so rₛ = 1 − 0.2 = 0.8.
- 2
Explain what a Spearman's rho value of 0.8 indicates.
Model answer
It indicates a strong positive correlation, since as ranks on one co-variable rise so do ranks on the other.
- 3
Why should a calculated value of rₛ never be greater than 1?
Model answer
A correlation coefficient runs only from −1 to +1, so a larger value shows an arithmetic error in the calculation.
- 4
State the formula for the chi-square statistic.
Model answer
It is χ² = Σ (O − E)² ÷ E, where O is each observed frequency and E is each expected frequency.
- 5
How are the degrees of freedom for a chi-square test calculated?
Model answer
Multiply one less than the number of rows by one less than the number of columns.
- 6
Calculate the degrees of freedom for a chi-square test on a table with two rows and three columns.
Model answer
The degrees of freedom are 2, because 1 multiplied by 2 gives 2.
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