. Author manuscript; available in PMC: 2022 May 1.

Published in final edited form as: Indoor Air. 2020 Dec 28;31(3):702–716. doi: 10.1111/ina.12760

Table 3:

Comparison of Model A3 prediction fit per pollutant

			Model A3: PM_2.5^†	Model A3: NO₂^‡	Model A3: NO_x^‡	Model A3: nicotine^‡
		Variables/groups	Est.	Est.	Est.	Est.
		(Intercept)	2.52^***	1.34^**	2.28^***	−5.49^***
City^§	(compared to “Ann Arbor” city)	Baltimore	0.06	0.03	0.59^**	1.4^***
		San Francisco	−0.01	0.21^**	−0.22	0.67^**
		Los Angeles	−0.48	−1.6E-03	−0.13	0.71
		New York	0.75^**	0.03	−0.15	0.13
		Salt Lake City	−0.10	−0.17	0.60^**	0.74
		Winston -Salem	−0.02	0.32^*	0.18	2.53^***
Meteorological measurements^§		Outdoor temperature in C° (2-week av.)	−3.10E-04		−0.01^***
Meteorological measurements^§		Outdoor RH (2-week av.)		−0.01^*		0.02
Proxy for infiltration estimation^§		PM_2.5 μg/m³ predicted infiltration	0.32
		NO₂ outdoor (ppb)		0.49^***
		NO_x outdoor (ppb)			0.32^***
Socio-economic factors (based on Census data)^§		% adults with education less than High School	0.02^**
		Median value ($) for specified owner-occupied housing units	6.7E-07
		Median family income		−3.14E-06 ^***
		% occupied housing units that are owner-occupied			−0.01^***	−3.4E-03
		Median household income			3.9E-06 ^**
Other pollutants measurements		PM_2.5 outdoor (μg/m³)		0.03^**	0.05^**
Smoking habits questions	N. cigarettes per day were smoked in the past year by any smoker in the house? (compared to “none” group)	Up to 20 cig.	1.07^***
		20 and more cig.	0.53^**
	Your approach to tobacco smoking in your home? (compared to “Never allow smoking in home” group)^¶	Allow smoking only in certain rooms	−0.36			0.51
		Allow smoking In all rooms	1.28^***			1.16^**
	Do you smoke cigarettes (as of one month ago)? (Y/N)^¶	Yes	0.99^***			1.06^***
	N. of cigarettes per day by each smoker. Is it more than 20 cigarettes? (Y/N)	Yes			0.45^**	1.82^***
	For how many years the allowing smoking at house approach?^¶	(in years)				4.9E-03
	Traveled by car with someone else who was smoking (during last week)? (Y/N)^¶	Yes				0.95^**
Building related questions	Age of building	(in years)	−2.64E-03	−8.5E-05	−9.7E-04	−0.01
	What floor do you live on? (compared to basement and ground floor)	2nd floor and higher	−1.19^***
	What type of building do you live in? (compared to “single family” type)	Rowhouse/townhouse/duplex/triplex				−0.33
		Apartment/condo				−0.57^*
		Manufact./mobile				−0.63
	What the garage is used for? (compared to “no garage”)	Parking 1 car	−0.21	0.28^**	0.23
		Parking 2 cars	−0.17	0.03	0.15
		Parking more than 2 cars	1.32^***	0.10	0.39^**
		Storage	−0.32	−0.07	−0.15
Cleaner appliances questions	Is an air cleaner/filter used? (Y/N)	Yes	−0.57^**
	Type of air cleaner/filter (Y/N)	Electrostatic precipitator (Yes)		−0.41^**
	How often is the air cleaner/filter used?	More than half of the days and less		−0.17
	How often is the air cleaner/filter used?	Almost daily or daily		0.08
Windows use questions	How often did you open the window (in summer)?	A few days a month		−0.19^**	−0.26^*	−1.10^***
		More than half of the days and less than daily		0.11	−0.10	−0.29
		Almost daily or daily		0.08	−0.11	−0.42
	Double pane windows (Y/N)	Yes		0.13
Heating sources questions	What are the heating sources used in your residence? (Y/N)	Fireplace wood (Yes)	3.68^***
		temperature: Fireplace gas	−0.19^***
		Fireplace gas (Yes)	−0.64^*
		Forced Air (vents)(Yes)		−0.15^**	−0.24^**
		Radiators (Yes)				1.21^**
Cooking habits questions	What type of oven is used? (compared to “electric” group)	Gas oven		0.24^**	0.37^**
	How often does someone cook (on stove) in residence? (compared to “not cooking” group)	Less than daily	−0.41	0.40^**	0.41^**
		Almost daily or daily	0.26	0.40^***	0.42^**
Pilots lights questions	The presence of a pilot lights on: (Y/N)	Oven (Yes)			0.15
		Water Heater (Yes)			−0.39^***
		Clothes Dryer (Yes)		0.32^***	0.52^***
Observations			195	223	230	192
R²/Adj. R²			0.60/0.54	0.63/0.57	0.58/0.53	0.61/0.56
AIC			569.64	282.47	468.72	647.55
Cross Validation R²(RMSE)			0.45 (1.06)	0.48 (0.47)	0.43 (0.69)	0.45 (1.37)

Notes:

^†

– Model A3 is based on PM_2.5 squared root function

^‡

- Model A3 is based on logarithmic function

^§

- These variables are mandatory and were included in each model regardless of the choice of stepwise regression.

^¶

– The questions that were obtained from Respiratory Diseases and Smoke Exposure questionnaire. Other questions related to house characteristics were obtained from Home Information Questionnaire.

^***

- p-value <=0.001;

^**

- p-value <0.05;

- p-value <0.1