Step 1
The standard error of the estimate s (or standard deviation of the residuals) represents the average error of predictions, thus the average deviation between actual y-values and the predicted y-values.
First, we sketch a scatterplot with a linear association and a large value of s.
For example, the following graph has a standard error exceeding 10, while there is no strong curvature in the scatterplot indicating a linear association.
Step 2
Next, we sketch a scatterplot with a nonlinear association and a smallvalue of s.
For example, the following graph has a smaller standard error that hte previous exercise, because the points vary lies about the sketched line.
Moreover, the relation is nonlinear as there is strong curvature present in the scatterplot.
Result:
Answers could vary.
Unusual points Each of the four scatterplots that follow shows a cluster of points and one “stray” point. For each, answer these questions:
1) In what way is the point unusual? Does it have high leverage, a large residual, or both?
2) Do you think that point is an influential point?
3) If that point were removed, would the correlation be- come stronger or weaker? Explain.
4) If that point were removed, would the slope of the re- gression line increase or decrease? Explain
The accompanying data on y = normalized energy \(\displaystyle{\left[{\left(\frac{{J}}{{m}^{{2}}}\right)}\right]}\) and x = intraocular pressure (mmHg) appeared in a scatterplot in the article “Evaluating the Risk of Eye Injuries: Intraocular Pressure During High Speed Projectile Impacts” (Current Eye Research, 2012: 43-49), an estimated regression function was superimposed on the plot.
\(\begin{array}{|c|c|}\hline x & 2761 & 19764 & 25713 & 3980 & 12782 & 19008 & 19028 & 14397 & 9606 & 3905 & 25731 \\ \hline y & 1553 & 14999 & 32813 & 1667 & 8741 & 16526 & 26770 & 16526 & 9868 & 6640 & 1220 & 30730 \\ \hline \end{array}\)
Here is Minitab output from fitting the simple linear regression model. Does the model appear to specify a useful relationship between the two variables?
\(\begin{array}{|c|c|}\hline \text{Predictor Coef SE Coef T P Constant} & -5090 & 2257 & -2.26 & 0.048 \\ \hline \text{Pressure} & 1.2912 & 0.1347 & 9.59 & 0.000 \\ \hline \end{array}\)
\([S=3679.36, R-Sq = 90.2\%, R-Sq(adj)=89.2\% ]\).
Make a scatterplot for the data.
Height and Weight of Females
Make a scatterplot for the data.
Height and Weight of Females