1. What is Pearson's PMCC?

Pearson's Product-Moment Correlation Coefficient (PMCC or r) measures the linear correlation between two variables X and Y. It ranges from -1 to +1, where 1 is total positive linear correlation, 0 is no linear correlation, and −1 is total negative linear correlation.

2. How to Calculate on Casio Calculator

Steps to calculate PMCC (r) on Casio calculator:

1. Press MODE then 2 to enter STAT mode
2. Select 2 for A+BX (linear regression)
3. Enter your X values, pressing = after each
4. Use arrow keys to move to Y column, enter Y values
5. Press AC when done entering data
6. Press SHIFT then 1 (STAT)
7. Press 7 (Reg)
8. Press 3 (r) to display correlation coefficient

3. Interpreting the Results

• r = 1: Perfect positive correlation
• r = -1: Perfect negative correlation
• r = 0: No linear correlation
• 0.7 ≤ |r| ≤ 1: Strong correlation
• 0.3 ≤ |r| < 0.7: Moderate correlation
• 0 < |r| < 0.3: Weak correlation

4. Using the Calculator

Instructions: Enter comma-separated X and Y values (must be same number of values). Example: "1, 2, 3, 4" for X and "2, 4, 6, 8" for Y.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between r and r²?
A: r measures strength and direction of linear relationship, while r² measures proportion of variance explained by the linear model.

Q2: What sample size is needed for reliable r?
A: Generally n ≥ 30 for stable estimates, but depends on effect size.

Q3: Does correlation imply causation?
A: No, correlation only measures association, not causation.

Q4: What if my data isn't linear?
A: Pearson's r only measures linear relationships. Consider Spearman's ρ for monotonic non-linear relationships.

Q5: How sensitive is r to outliers?
A: Pearson's r can be strongly affected by outliers. Always examine your data visually.