Table 3.

Beta coefficients (P-values in parentheses) for multiple linear regression models predicting the impact of each postcard mailing on average weekly soil moisture, controlling for soil compaction and city watering. All regression models include the week prior to the postcard mailing and the week in which the postcard was mailed.

Regression model1234567
Postcard234z5678
Weeks2, 3y4, 6y4, 7yx8, 9yx10x, 11y12w, 13y15, 16y
1. Constant0.21
(0.00)
***		0.23
(0.00)
***		0.23
(0.00)
***		0.16
(0.00)
***		0.20
(0.00)
***		0.25
(0.00)
***		0.16
(0.00)
***
2. Week0.01
(0.51)		−0.03
(0.10)		0.04
(0.01)
***		0.07
(0.00)
***		0.07
(0.00)
***		−0.02
(0.27)		0.05
(0.01)
***
3. Postcard received0.02
(0.14)		−0.02
(0.21)		−0.02
(0.24)		0.03
(0.11)		0.01
(0.47)		0.00
(0.92)		−0.01
(0.50)
4. Postcard-week−0.01
(0.70)		0.05
(0.02)

**		0.05
(0.04)

**		−0.02
(0.46)		−0.03
(0.22)		−0.02
(0.45)		0.00
(0.96)
5. Soil compaction0.003
(0.03)
**		0.002
(0.18)		0.001
(0.42)		0.005
(0.01)
***		0.002
(0.27)		0.000
(0.83)		0.002
(0.18)
6. City watering----0.01
(0.53)		0.01
(0.44)		−0.02
(0.46)		−0.02
(0.44)		--
N158161162157162162162
R0.240.220.480.410.340.230.34
R20.060.050.230.170.120.050.12
Adj. R20.030.020.210.140.090.020.09
F2.241.889.416.024.081.725.12
P-value0.07
*		0.120.00
***		0.00
***		0.00
***		0.130.00
***

  • ↵z This regression model included week seven (when the postcard was mailed) and week four, the last previous week in which a postcard had not been mailed.

  • ↵y Indicates the week the postcard was mailed and the week dummy variable that was entered into the regression model.

  • ↵x Indicates the week in which some of the trees were watered by the city.

  • Note: Double asterisk (**) indicates P < 0.05; triple asterisk (***) indicates P < 0.01.