Answer:
c. Observed data points that are far from the other observed data points in the horizontal direction
True, by definition are observed data points that are far from the other observed data points in the horizontal direction.
Explanation:
When we conduct a regression we consider influential points by definition "an outlier that greatly affects the slope of the regression line". Based on this case we can analyze one by one the possible options:
a. Observed data points that are close to the other observed data points in the horizontal direction
False. If are close to the other observed values then are not influential points
b. Observed data points that are far from the least squares line
False, that's the definition of outlier.
c. Observed data points that are far from the other observed data points in the horizontal direction
True, by definition are observed data points that are far from the other observed data points in the horizontal direction.
d. Observed data points that are close to the least squares line
False. If are close to the fit regression line adjusted then not affect the general equation for the model and can't be considered as influential points