Table 2.

Substance Problem Scale Items and Rasch Statistics

Item-Label	Substance Problem Scale (SPS) questions\b. When was the last time…	Rasch		INFITc		OUTFITd
		Measurea	Rankb	MNSQe	ZSTDf	MNSQ	ZSTD
1–Hideuse	you tried to hide that you were using alcohol or drugs?	−0.45	13	1.42	9.9	1.78	9.9
2–Complaints	your parents, family, partner, co–workers, classmates or friends, complained about your alcohol or drug use?	−0.89	15	1.2	9.9	1.39	9.9
3–Weeklyuse	you used alcohol or drugs weekly?	−1.13	16	0.93	−4.3	1.04	1.5
4–MentHlth	your alcohol or drug use caused you to feel depressed, nervous, suspicious, uninterested in things, reduced your sexual desire or caused other psychological problems?	0.19	7	0.95	−3.4	0.9	−4.3
5–PhysHlth	your alcohol or drug use caused you to have numbness, tingling, shakes, blackouts, hepatitis, TB, sexually transmitted disease or any other health problems?	1.29	1	1.26	9.9	1.13	3.3
6–Role	you kept using alcohol or drugs even though you knew it was keeping you from meeting your responsibilities at work, school, or home?	−0.19	11	0.78	−9.9	0.75	−9.9
7–Hazrd	you used alcohol or drugs where it made the situation unsafe or dangerous for you, such as when you were driving a car, using a machine, or where you might have been forced into sex or hurt?	0.37	4	1.06	3.7	1.09	3.3
8–Legal	your alcohol or drug use caused you to have repeated problems with the law?	0.55	3	1.53	9.9	1.75	9.9
9–Trouble	you kept using alcohol or drugs even though it was causing social problems, leading to fights, or getting you into trouble with other people?	−0.39	12	1.08	5.1	1.16	7.3
10–Tolerance	you needed more alcohol or drugs to get the same high or found that the same amount did not get you as high as it used to?	0.14	8	0.84	−9.9	0.77	−9.8
11–Wdrawal	you had withdrawal problems from alcohol or drugs like shaking hands, throwing up, having trouble sitting still or sleeping, or that you used any alcohol or drugs to stop being sick or avoid withdrawal problems?	0.63	2	1.1	5.8	0.95	−1.9
12–LosCon	you used alcohol or drugs in larger amounts, more often or for a longer time than you meant to?	−0.14	10	0.77	−9.9	0.75	−9.9
13–Nostop	you were unable to cut down or stop using alcohol or drugs?	0.12	9	0.93	−4.8	0.88	−4.7
14–Time	you spent a lot of time either getting alcohol or drugs, using alcohol or drugs, or feeling the effects of alcohol or drugs (high, sick)?	−0.63	14	0.78	−9.9	0.75	−9.9
15–ReducActs	your use of alcohol or drugs caused you to give up, reduce or have problems at important activities at work, school, home or social events?	0.27	5	0.8	−9.9	0.79	−9.9
16–DespiteHlth	you kept using alcohol or drugs even after you knew it was causing or adding to medical, psychological or emotional problems you were having?	0.26	6	0.86	−9.3	0.89	−9.9

^aMeasure is the Rasch estimated logits of a given item from the mean of items on the latent SPS dimension.

^bRank is the rank order (low to high) of items.

^cItem INFIT is the overall agreement of the item’s with the model prediction in this data where high values suggest more random than expected and low values suggest everyone answers the item the same (e.g., all the same).

^dItem OUTFIT is a measure of how precisely the item severity measure predicts individuals’ answers to the item, where high values means that item response curve is flatter than average and/or crosses over other item curves and low values mean that the item is closer to a step function that provides little information just below or above the cut point to help the overall estimate of a continuous dimension.

^eMNSQ is the average squared deviation of the difference between individual responses and the predict response for the item.

^fZSTD is the MNSQ standardized into Z–score based on the mean/variance of MNSQ for the items in the table.

Note: SPS Items reproduced with permission of copyright holder (Chestnut Health Systems), see www.chestnut.org/li/gain for complete copy of the GAIN