Refer to the water-discharge data given in Exercise 55 and let y
ln(q), x1
ln(a), and x2
ln(b). Consider fitting the model Y
0 1x1 2x2 !.

a. The resulting hiis are .138, .302, .266, .604, .464, .360,

.215, .153, .214, and .284. Does any observation appear to be influential?

b. The estimated coefficients are ˆ

0
1.5652, ˆ

1
.9450,

ˆ

2
.1815, and the corresponding estimated standard deviations are sˆ

0
.7328, sˆ

1
.1528, and sˆ

2
.1752. The second standardized residual is e*2
2.19. When the second observation is omitted from the data set, the resulting estimated coefficients are ˆ

0
1.8982, ˆ

1
1.025, and

ˆ

2
.3085. Do any of these changes indicate that the second observation is influential?

c. Deletion of the fourth observation (why?) yields

ˆ

0
1.4592, ˆ

1
.9850, and ˆ

2
.1515. Is this observation influential?