The regression equation given is:

$y = -0.0495x + 6.6$

where $y$ represents the age difference (husband's age minus wife's age) and $x$ represents the literacy rate (percent of the population that is literate).

Interpretation of the slope:

The slope of the regression line is $-0.0495$. This indicates that for every unit increase in literacy rate, the age difference falls by 0.0495 units, on average.

Thus, the correct interpretation is:

For every unit increase in literacy rate, the age difference falls by 0.0495 units, on average.

Summary:

• Slope: $-0.0495$ implies a negative relationship between literacy rate and age difference.
• Interpretation: As literacy rate increases, the age difference decreases.

Would you like further details or clarification? Here are some related questions for deeper understanding:

1. What does the intercept $6.6$ represent in this context?
2. How would you interpret the prediction for a country with 80% literacy rate?
3. What is the significance of the range $24 \leq x \leq 100$ in this model?
4. How can the residuals help assess the fit of this model?
5. What assumptions must be met for this linear regression to be valid?

Tip: Always check if the slope sign matches the expected direction of the relationship in real-world context!