Stat and Data Analysis 68 pts Name: KEY
4.1 Outlier Effects
1. Graph the following points. Find the mean and standard deviation of each set and the correlation.
x / 1 / 2 / 3 / 4 / 5 / 6y / 2 / 4 / 3 / 7 / 5 / 8
A. Now include the point (4,5). Mark the point on the graph as point A. Where is the point in relation to the original points? Recalculate the correlation. What happened?
In the middle of the scatterplot
r = 0.8514; Stayed the same
B. Change the point to (8,9). Mark the point on the graph as point B. Where is the point in relation to the original points? Recalculate the correlation. What happened?
Outlier in x and y and within the pattern
r = 0.9066; Increased/Strengthened
C. Change the point to (14,16). Mark the point on the graph as point C. Where is the point in relation to the original points? Recalculate the correlation. What happened?
Far outlier in x and y and within the pattern
r = 0.9724; Increased/Strengthened
D. Change the point to (10,5). Mark the point on the graph as point D. Where is the point in relation to the original points? Recalculate the correlation. What happened?
Outlier in the x but not the y, not a part of the pattern
r = 0.5115; Decreased/Weakened
E. Change the point to (18,5). Mark the point on the graph as point E. Where is the point in relation to the original points? Recalculate the correlation. What happened?
Far outlier in the x but not in the y, not a part of the pattern
r = 0.2823; Decreased/Weakened
F. Change the point to (5,14). Mark the point on the graph as point F. Where is the point in relation to the original points? Recalculate the correlation. What happened?
Far outlier in the y but not the x, not a part of the pattern
r = 0.6911; Decreased/Weakened
G. Change the point to (1,10). Mark the point on the graph as point G. Where is the point in relation to the original points? Recalculate the correlation. What happened?
Outlier in the x and y, not a part of the pattern
r = 0.2204; Decreased/Weakened
2. Graph the following points. Find the mean and standard deviation of each set and the correlation.
x / 6 / 7 / 8 / 9 / 10 / 11y / 12 / 14 / 13 / 10 / 9 / 8
A. Now include the point (1,18). Mark the point on the graph as point A. Where is the point in relation to the original points? Recalculate the correlation. What happened?
Outlier in both x and y, with the pattern
r = -0.9436; Decreased/Strengthened
B. Change the point to (17,6). Mark the point on the graph as point B. Where is the point in relation to the original points? Recalculate the correlation. What happened?
Outlier both x and y, somewhat with of the pattern
r = -0.8846; Decreased slightly/Strengthened slightly
C. Change the point to (14,16). Mark the point on the graph as point C. Where is the point in relation to the original points? Recalculate the correlation. What happened?
Outlier in both x and y, Not with the pattern
r = 0.0987; Increased/Weakened – Changed direction
D. Change the point to (1,1). Mark the point on the graph as point D. Where is the point in relation to the original points? Recalculate the correlation. What happened?
Outlier in both x and y, Not with the pattern
r = 0.5239; Increased/Weakened – Changed direction
E. Change the point to (8,11). Mark the point on the graph as point E. Where is the point in relation to the original points? Recalculate the correlation. What happened?
In the middle of the x’s and y’s
r = -0.8531; Stayed about the same
F. Change the point to (8,19). Mark the point on the graph as point F. Where is the point in relation to the original points? Recalculate the correlation. What happened?
Outlier in the y but not the x, Not with the pattern
r = -0.5854; Increased/Weakened
G. Change the point to (19,10). Mark the point on the graph as point G. Where is the point in relation to the original points? Recalculate the correlation. What happened?
Outlier in x but not y, Not with the pattern
r = -0.4925; Increased/Weakened
3. Graph the following points. Find the mean and standard deviation of each set and the correlation.
x / 6 / 7 / 8 / 9 / 7 / 8y / 12 / 14 / 13 / 10 / 10 / 11
A. Now include the point (1,18). Mark the point on the graph as point A. Where is the point in relation to the original points? Recalculate the correlation. What happened?
Outlier in x and y in the upper left corner
r = -0.8582; Decreased/Strengthened
B. Change the point to (17,18). Mark the point on the graph as point B. Where is the point in relation to the original points? Recalculate the correlation. What happened?
Outlier in x and y in the upper right corner
r = 0.7725; Increased/Strengthened
C. Change the point to (14,4). Mark the point on the graph as point C. Where is the point in relation to the original points? Recalculate the correlation. What happened?
Outlier in x and y in the lower right corner
r = -0.8867; Decreased/Strengthened
For each of the following graphs state whether the correlation would weaken, strengthen, or stay about the same if the marked points were removed. (1 point for each point)
1. 2.
A – Weaken A – Weaken
B – Strengthen B – Strengthen
C – Stay the Same C – Stay the Same