PROMIS® Reference Populations

PROMIS measures use scores that have meaning. A PROMIS score of 50 is the average (or mean) score for a specific, relevant group of people (e.g., the U.S. general population, kids with a painful condition). That group is the reference population.

 

PROMIS measures use scores that are more than just numbers: PROMIS scores have meaning. For example, a PROMIS measure score of 50 is the mean score for that measure. But average for whom? This is where “score meaning” comes in. Each PROMIS measure has its own reference population, that is, its own specific group of people (e.g., the U.S. general population, kids with a painful condition) who have been sampled and then thoroughly assessed with the PROMIS measure. The average score of 50 for that PROMIS measure is their average score. Thus, when someone is newly assessed with a PROMIS measure, and we observe that her score is 50, we have a score value, and we can say that her score is the same score as the average score for the PROMIS measure’s reference population – the population group to which we turn to or refer for score meaning.

Reference Populations

A T-score is a standardized score, like z-scores and IQ scores. All standardized scores have a “middle” score; it is zero for z-scores, 100 for IQ scores, and 50 for T-scores. This middle score is the mean of a large sample that is representative of a relevant population—a reference population. The large sample used to represent the reference population is called the Centering Sample.

For some PROMIS measures the reference population (and the centering sample) was a clinical population. This is the case for PROMIS Smoking measures, for which the reference populations was daily smokers; the centering sample was a sample of daily smokers. For many PROMIS measures, the reference population was the 2000 General US Census. The centering sample was a large sample of individuals who represented the 2000 US General Census.

Centering Sample and Calibration Sample

It is helpful to remember that the middle score of a standard score range has to be defined. For measures that use a T-score metric, 50 is the mean and 10 is the standard deviation, but they do not start out that way. The scores are first estimated using an item response model and the IRT-calibrated scores are transformed to a T-score metric using a linear transformation. But first you have to decide which score on the IRT metric is going to be the middle score—a score of 50. This is done by collecting scores from a large sample that represents the reference population and then calculating the mean for that sample. That sample is the centering sample.  That score becomes the middle score (e.g., 50 for T-scores). A linear transformation spaces all other scores along the continuum so they have the correct values relative to the middle score (mean of the centering sample) used to represent the middle score.

IMPORTANT: The Centering Sample and the Calibration Sample may not be the same sample.

The purpose of a calibration sample is to estimate item parameters (item characteristics such as difficulty and discrimination) using an item response theory model. Here’s where it can get confusing. Sometimes a single sample was used as both the calibration sample AND the centering sample. Other times one sample was used as the calibration sample and another was used as the centering sample.  Sometimes, a subset of the calibration sample served as the centering sample.

The Reference Population tables show the calibration and the centering samples for PROMIS. Most users will be particularly interested in the last column (Centering Sample). If you want to know what a score in the middle is (e.g., 50 for those scored on a T-score metric), go to the Centering Sample column. For example, if you go to the row for PROMIS-Cancer-Anxiety you will see that the item parameters were estimated (calibrated) using a hybrid of individuals with cancer and individuals from the general population. BUT, the centering sample was the general population. A score of 50 on this measure is comparable to the general population average level of anxiety.

What does the middle score mean?

When developing a measure with standard scores, an important consideration is what the middle score means. The scores of such measure are purposefully “centered” at the mean of a specific sample or subsample. PROMIS uses T-score, so the middle score is always 50. Centering scores in this way allows quick interpretation of where an individual is on a symptom or outcome compared to others in the reference population. A score of 50 on PROMIS Fatigue, for example, is comparable to the U.S. “average”. T-scores have a standard deviation of 10, so a score of 60 would indicate fatigue that is a standard deviation higher than the U.S. average.

TIP : Failure to be specific about the reference population invites confusion.


This can all get very confusing because sometimes the calibration sample (the sample used to estimate item response theory parameters) and centering sample (the sample used to define the middle of the score range) were the same. But sometimes they were different. For example, a measure may be calibrated in a clinical sample but then centered in the general population. The mean of T=50 for that measure reflects the average in the general population, not the clinical sample.

 PROMIS Adult
Item Bank/ScaleCalibration SampleCentering Sample
Global MentalGeneral populationGeneral population
Global PhysicalGeneral populationGeneral population
Emotional Distress - AngerGeneral populationGeneral population
Emotional Distress - AnxietyGeneral PopulationGeneral population
   PROMIS-Cancer - AnxietyHybrid*General population
Emotional Distress - DepressionGeneral populationGeneral population
   PROMIS-Cancer - DepressionHybrid*General population
Cognitive Function (v2.0)General PopulationGeneral population
Cognitive Function - AbilitiesGeneral PopulationGeneral population
Psychosocial Illness Impact - PositiveClinical sample (cancer)Clinical sample (cancer)
Psychosocial Illness Impact - NegativeClinical sample (cancer)Clinical sample (cancer)
Self-Efficacy - GeneralGeneral populationGeneral population
Self-Efficacy - Manage EmotionsClinical sampleClinical sample
Self-Efficacy - Manage Meds/TreatmentClinical sampleClinical sample
Self-Efficacy - Manage Social InteractionsClinical sampleClinical sample
Self-Efficacy - Manage Daily ActivitiesClinical sampleClinical sample
Self-Efficacy - Manage SymptomsClinical sampleClinical sample
Alcohol - Alcohol UseGeneral population subset + Clinical sampleGeneral population subset + Clinical sample
Alcohol - Positive ConsequencesGeneral population subset + Clinical sampleGeneral population subset + Clinical sample
Alcohol - Negative ConsequencesGeneral population subset + Clinical sampleGeneral population subset + Clinical sample
Alcohol - Negative ExpectanciesGeneral population subset + Clinical sampleGeneral population subset + Clinical sample
Smoking - Coping ExpectanciesClinical sample (smokers drawn from the general population)Daily smokers
All Smokers; Daily Smokers; Nondaily SmokersClinical sample (smokers drawn from the general population)Daily smokers
Smoking – Emotional/Sensory ExpectanciesClinical sample (smokers drawn from the general population)Daily smokers
All Smokers; Daily Smokers; Nondaily SmokersClinical sample (smokers drawn from the general population)Daily smokers
Smoking – Negative Health ExpectanciesClinical sample (smokers drawn from the general population)Daily smokers
All Smokers; Daily Smokers; Nondaily SmokersClinical sample (smokers drawn from the general population)Daily smokers
Smoking – Nicotine DependenceClinical sample (smokers drawn from the general population)Daily smokers
All Smokers; Daily Smokers; Nondaily SmokersClinical sample (smokers drawn from the general population)Daily smokers
Smoking – Negative Psychosocial ExpectanciesClinical sample (smokers drawn from the general population)Daily smokers
All Smokers; Daily Smokers; Nondaily SmokersClinical sample (smokers drawn from the general population)Daily smokers
Smoking – Social MotivationsClinical sample (smokers drawn from the general population)Daily smokers
All Smokers; Daily Smokers; Nondaily SmokersClinical sample (smokers drawn from the general population)Daily smokers
Substance Use - AppealClinical and non-clinical substance usersClinical and non-clinical substance users
Past 30 days - Past 3 monthsClinical and non-clinical substance usersClinical and non-clinical substance users
Substance Use - SeverityClinical and non-clinical substance usersClinical and non-clinical substance users
Past 30 days - Past 3 monthsClinical and non-clinical substance usersClinical and non-clinical substance users
Substance Use - Prescription Pain Medication MisuseParticipants who reported possession of a prescription for pain medication and potential misuse of such a medicationParticipants who reported possession of a prescription for pain medication and potential misuse of such a medication
Life SatisfactionGeneral populationGeneral population
Meaning and PurposeGeneral populationGeneral population
Positive AffectGeneral populationGeneral population
FatigueGeneral populationGeneral population
   PROMIS-Cancer - FatigueGeneral populationGeneral population
Pain - BehaviorGeneral population + Clinical sampleGeneral population
Pain - InterferenceGeneral Population + Clinical sampleGeneral population
   PROMIS-Cancer - Pain InterferenceHybrid*General population
Pain IntensityGeneral population + clinical samplePeople with pain drawn from the general population and pain support groups
Physical FunctionGeneral populationGeneral population
   PROMIS-Cancer - Physical FunctionHybrid*General population
   - MobilityGeneral populationGeneral population
   - Upper ExtremityGeneral populationGeneral population
Physical Function for Samples with Mobility Aid UsersClinical SampleClinical Sample
Sleep DisturbanceGeneral population + Clinical sampleGeneral population + Clinical sample
Sleep-Related ImpairmentGeneral population + Clinical sampleGeneral population + Clinical sample
Sexual Function and Satisfaction** (v1.0): Global Satisfaction with Sex LifeSexually active general populationSexually active general population
Sexual Function and Satisfaction: Interest in Sexual Activity ** (v1.0)Sexually active general populationSexually active general population
Sexual Function and Satisfaction: Lubrication ** (v1.0)Sexually active general populationSexually active general population
Sexual Function and Satisfaction: Vaginal Discomfort **(v1.0)Sexually active general populationSexually active general population
Sexual Function and Satisfaction: Erectile Function **Sexually active general populationSexually active general population
Sexual Function and Satisfaction: Orgasm (uncalibrated item pool)NANA
Sexual Function and Satisfaction: Therapeutic Aids (uncalibrated item pool)NANA
Sexual Function and Satisfaction: Sexual Activities (uncalibrated item pool)NANA
Sexual Function and Satisfaction: Anal Discomfort (uncalibrated item pool)NANA
Sexual Function and Satisfaction: Anal Discomfort (uncalibrated item pool)NANA
Sexual Function and Satisfaction: Interfering Factors (uncalibrated item pool)NANA
Sexual Function and Satisfaction Screener Questions (uncalibrated item pool)NANA
Satisfaction with Participation in Discretionary Social Activities (v1.0)General populationGeneral population
Satisfaction with Participation in Social Roles and Activities (v1.0)General populationGeneral population
Satisfaction with Social Roles and Activities (v2.0)General populationGeneral population
Ability to Participate in Social Roles and ActivitiesGeneral populationGeneral population
CompanionshipGeneral populationGeneral population
Informational SupportGeneral populationGeneral population
Emotional SupportGeneral populationGeneral population
Instrumental SupportGeneral populationGeneral population
Social IsolationGeneral populationGeneral population
Dyspnea – Activity MotivationNA - PoolNA - Pool
Dyspnea – Activity RequirementsNA - PoolNA - Pool
Dyspnea – Airborne ExposureNA - PoolNA - Pool
Dyspnea – Assistive DevicesNA - PoolNA - Pool
Dyspnea – CharacteristicsNA - PoolNA - Pool
Dyspnea – Emotional ResponseNA - PoolNA - Pool
Dyspnea – Functional LimitationsCOPD SampleCOPD Sample
Dyspnea – Task AvoidanceNA - PoolNA - Pool
Dyspnea – Time ExtensionNA - PoolNA - Pool
Dyspnea – SeverityCOPD SampleCOPD Sample
Gastrointestinal – Belly PainGI Sample (clinical sample + general population who reported at least 1 GI symptom)General Population who reported at least 1 GI symptom
Gastrointestinal – Bowel IncontinenceNA - PoolNA - Pool
Gastrointestinal – ConstipationGI Sample (clinical sample + general population who reported at least 1 GI symptom)General Population who reported at least 1 GI symptom
Gastrointestinal – DiarrheaGI Sample (clinical sample + general population who reported at least 1 GI symptom)General Population who reported at least 1 GI symptom
Gastrointestinal – Disrupted SwallowingGI Sample (clinical sample + general population who reported at least 1 GI symptom)General Population who reported at least 1 GI symptom
Gastrointestinal – Gas and BloatingGI Sample (clinical sample + general population who reported at least 1 GI symptom)General Population who reported at least 1 GI symptom
Gastrointestinal – Gastroesophageal RefluxGI Sample (clinical sample + general population who reported at least 1 GI symptom)General Population who reported at least 1 GI symptom
Gastrointestinal – Nausea and VomitingGI Sample (clinical sample + general population who reported at least 1 GI symptom)General Population who reported at least 1 GI symptom
Pain Quality – Neuropathic PainClinical sample with painful conditionsClinical sample with painful conditions
Pain Pain Quality – Nociceptive PainClinical sample with painful conditionsClinical sample with painful conditions
Sexual Function and Satisfaction: Anal Discomfort with Sexual Activity (for Sexually Active People)NA - PoolNA - Pool
Sexual Function and Satisfaction: Erectile Function (for Sexually Active Men)Sexually active men from the general population and men with sexual dysfunctionSexually active men
Sexual Function and Satisfaction: Factors Interfering with Sexual SatisfactionNA - PoolNA - Pool
Sexual Function and Satisfaction: Interest in Sexual ActivityNA - PoolNA - Pool
Sexual Function and Satisfaction: Oral Discomfort with Sexual Activity (for Sexually Active People)Sexually active adults from the general population and adults with sexual dysfunctionSexually active adults
Sexual Function and Satisfaction: Oral Discomfort with Sexual Activity (for Sexually Active People)Sexually active adults from the general population and adults with sexual dysfunctionSexually active adults
Sexual Function and Satisfaction: Oral Dryness with Sexual Activity (for Sexually Active People)Sexually active adults from the general population and adults with sexual dysfunctionSexually active adults
Sexual Function and Satisfaction: Orgasm – Ability (for Sexually Active People)Sexually active adults from the general population and adults with sexual dysfunctionSexually active adults
Sexual Function and Satisfaction: Orgasm – Ability (for Sexually Active People)Sexually active adults from the general population and adults with sexual dysfunctionSexually active adults
Sexual Function and Satisfaction: Orgasm - Pleasure (for Sexually Active People)Sexually active adults from the general population and adults with sexual dysfunctionSexually active adults
Sexual Function and Satisfaction: Satisfaction with Sex LifeSexually active adults from the general population and adults with sexual dysfunctionSexually active adults
Sexual Function and Satisfaction: ScreenersNA - PoolNA - Pool
Sexual Function and Satisfaction: Sexual Activities (Male and Female measures)NA - PoolNA - Pool
Sexual Function and Satisfaction: Therapeutic Aids for Sexual Activity (Male and Female measures)NA - PoolNA - Pool
Sexual Function and Satisfaction: Vaginal Discomfort with Sexual Activity (for Sexually Active Women)Sexually active adults from the general population and adults with sexual dysfunctionSexually active women
Sexual Function and Satisfaction: Vaginal Lubrication for Sexual Activity (for Sexually Active Women)Sexually active adults from the general population and adults with sexual dysfunctionSexually active women
Sexual Function and Satisfaction: Vulvar Discomfort with Sexual Activity – Clitoral (for Sexually Active Women)Sexually active adults from the general population and adults with sexual dysfunctionSexually active women
Sexual Function and Satisfaction: Vulvar Discomfort with Sexual Activity – Labial (for Sexually Active Women)Sexually active adults from the general population and adults with sexual dysfunctionSexually active women

* Hybrid: items that did not have DIF between general population and cancer patients used the PROMIS parameters. DIF items used cancer-based parameters. All items included in fatigue item bank did not have DIF and thus all used PROMIS parameters

** Sexual function related item bank: qualitative related components were conducted using clinical sample but data from sexually active general population was used for parameter estimations.

*** Only banks that used a different sample from the calibration sample for centering were documented in this column.

 PROMIS Pediatric
Bank/ScaleCalibration SampleCentering Sample
Global Health*General populationGeneral population
Emotional Distress - AngerGeneral population subset + Clinical sampleGeneral population subset + Clinical sample
Emotional Distress - AnxietyGeneral population subset + Clinical sampleGeneral population subset + Clinical sample
Emotional Distress - DepressionGeneral population subset + Clinical sampleGeneral population subset + Clinical sample
Cognitive FunctionGeneral populationGeneral population
Life SatisfactionGeneral populationGeneral population
Meaning and PurposeGeneral populationGeneral population
Psychological Stress ExperiencesGeneral populationGeneral population
Positive AffectGeneral populationGeneral population
FatigueGeneral population subset + Clinical sampleGeneral population subset + Clinical sample
Pain - BehaviorClinical sample
(Children with painful conditions)
Clinical sample (Children with painful conditions)
- MobilityGeneral population subset + Clinical sampleGeneral population subset + Clinical sample
- Upper ExtremityGeneral population subset + Clinical sampleGeneral population subset + Clinical sample
Sleep DisturbanceGeneral populationGeneral population
Sleep-Related ImpairmentGeneral populationGeneral population
Physical ActivityGeneral populationGeneral population
Physical Stress ExperienceGeneral populationGeneral population
Strength ImpactGeneral populationGeneral population
Asthma ImpactClinical sampleClinical sample
Peer RelationshipsGeneral population subset + Clinical sampleGeneral population subset + Clinical sample
Pain QualityChildren with painful conditionsChildren with painful conditions
Pain Quality - AffectiveChildren with painful conditionsChildren with painful conditions
Pain Quality - SensoryChildren with painful conditionsChildren with painful conditions
Family RelationshipsGeneral PopulationGeneral Population

* Hybrid: items that did not have DIF between general population and cancer patients used the PROMIS parameters. DIF items used cancer-based parameters. All items included in fatigue item bank did not have DIF and thus all used PROMIS parameters

** Sexual function related item bank: qualitative related components were conducted using clinical sample but data from sexually active general population was used for parameter estimations.

*** Only banks that used a different sample from the calibration sample for centering were documented in this column.

 PROMIS Parent Proxy
Bank/ScaleCalibration SampleCentering Sample
Global Health*General populationGeneral population
Emotional Distress - AngerGeneral population subset + Clinical sampleGeneral population subset + Clinical sample
Emotional Distress - AnxietyGeneral population subset + Clinical sampleGeneral population subset + Clinical sample
Emotional Distress - DepressionGeneral population subset + Clinical sampleGeneral population subset + Clinical sample
Cognitive FunctionGeneral populationGeneral population
Life SatisfactionGeneral populationGeneral population
Meaning and PurposeGeneral populationGeneral population
Psychological Stress ExperiencesGeneral populationGeneral population
Positive AffectGeneral populationGeneral population
FatigueGeneral population subset + Clinical sampleGeneral population subset + Clinical sample
Pain - BehaviorClinical sample
(Children with painful conditions)
Clinical sample (Children with painful conditions)
Pain - InterferenceGeneral population subset + Clinical sampleGeneral population subset + Clinical sample
- MobilityGeneral population subset + Clinical sampleGeneral population subset + Clinical sample
- Upper ExtremityGeneral population subset + Clinical sampleGeneral population subset + Clinical sample
Sleep DisturbanceGeneral populationGeneral population
Sleep-Related ImpairmentGeneral populationGeneral population
Physical ActivityGeneral populationGeneral population
Physical Stress ExperienceGeneral populationGeneral population
Strength ImpactGeneral PopulationGeneral Population
Asthma ImpactClinical sampleClinical sample
Peer RelationshipsGeneral population subset + Clinical sampleGeneral population subset + Clinical sample
Pain QualityChildren with painful conditionsChildren with painful conditions
Pain Quality - AffectiveChildren with painful conditionsChildren with painful conditions
Pain Quality - SensoryChildren with painful conditionsChildren with painful conditions
Family RelationshipsGeneral PopulationGeneral Population

* Hybrid: items that did not have DIF between general population and cancer patients used the PROMIS parameters. DIF items used cancer-based parameters. All items included in fatigue item bank did not have DIF and thus all used PROMIS parameters

** Sexual function related item bank: qualitative related components were conducted using clinical sample but data from sexually active general population was used for parameter estimations.

*** Only banks that used a different sample from the calibration sample for centering were documented in this column.

Norms

A unique aspect of PROMIS measures is their use of standardized scores that are centered on a relevant reference population. Such scores are called “normative” because their value represents how close or far away they are from a normative population. The word “norm” has different meanings for different contexts. Here, we are not talking about social “norms,” the behaviors we expect from others and ourselves in society. We are also not talking about “normal” per se, even though the term originated from its reference to a standard, bell-shaped distribution curve that labels everything in the vast middle as normal. We use the word norm without applying judgment as to the “normality” of any given score relative to the distribution of scores seen on the same measure in a large group of people. Sometimes we refer to the group as a “reference group” and similarly to “norms” as reference values , because they are points of reference from which to understand a given single score.

For example, Jensen et al published reference values for eight PROMIS domains for individuals with cancer. The mean Pain Interference score for people with cancer was 52. Learn more>>

For some PROMIS measures there are subpopulation norms.

Subpopulation Norms

Norms are based on the distribution of scores on a measure for a well-characterized and relevant population. For example, I am 5’6” tall. I might be interested in comparing my height to other people in the world, or maybe just the United States since that’s where I live. On the other hand, I am a woman and so average height without considering gender doesn’t really matter to me. I would be interested in knowing my height relative to other women in the United States. So I might be interested in comparing my height to the mean height of other persons in the United States. According to Wikipedia, the average height for women in the United States is 5’4” and therefore I’m feeling pretty tall right now. I would not feel quite so tall if I were comparing myself to men in the United States (5’9”); and, I would only be eye-to-eye with the average woman in the Netherlands (5’6”), which brings us, finally to normative score comparisons for health outcomes measures.

Let’s start with a distinction between norms that are used for comparative purposes and norms that are used to anchor a scale. Many of the PROMIS measures (see elsewhere on this site) are centered on the mean score of a sample of individuals that, collectively, matched the US 2000 General Census with respect to important demographics (e.g., gender, age, race/ethnicity, education). The beauty of folding the norms into the metric is that it is easy to interpret a score relative to the population whose norm was used. With the PROMIS scores that are centered on the US Census population, the mean is 50 and standard deviation is 10. So, if my fatigue score is 60, I know that I’m not just feeling tired; my fatigue is one standard deviation above the general population (or at least a sample that matched it). But, as of this writing, I’m 62 years old. I’d like to know how my fatigue compares to people my age. That’s where sub-norms can be helpful.

Sub-norms divide a relevant population into subgroups to aid interpretation of scores. Above, I compared my height to that of women in the US, not to all people in the world or even to all people in the US. I found it more relevant to compare my height to a sub-norm value—the mean height of women in the US.

It is theoretically possible to develop sub-norms for scores for a measure based on any relevant population; though such data collection can be expensive. As HealthMeasures continued be used and more data accumulates, however, it may become practical to develop many sub-norms for comparing and interpreting scores.

Fortunately, the initial norming sample for PROMIS was quite large and it was feasible to disaggregate by gender and age ranges in order to estimate sub-group norms. This was done in 2011 for comparing the fatigue and pain by age range in the general population to that of samples of individuals with disabilities. The gender and age range norms were calculated for all PROMIS measures developed in the first phase of PROMIS testing. These were never published but are provided here for users who are interested. Means, standard deviations, and frequencies by domain are reported in the tables below.

WARNING

The original PROMIS norming sample was not powered to develop subgroup norms. The user should pay particular attention to the size and characteristics of the sample used to develop each sub-norm. For example, much larger samples were used to calculate sub-norms for males and females than for the age ranges. More confidence is warranted for sub-norms estimated with larger sample sizes. Nevertheless, these sub-norms can be useful both in comparing samples and interpreting scores. For reference, consider how they were used in papers by Cook et al, and Molton et al.

Gender and Age Range Sub-norms for Adult PROMIS Measures Centered on the US General Census 2000

Domain GenderAge in Years
 FemaleMale18-3435-4445-5455-6465-7475+
AngerN18651204730565499495401379
Mean50.649.153.051.550.448.847.545.7
SD10.29.610.710.39.59.78.77.9
AnxietyN16541069659496417442365345
Mean50.948.652.450.950.149.348.146.9
SD10.29.510.711.19.59.58.87.9
DepressionN1269890496366359373290276
Mean50.948.752.350.650.849.548.446.5
SD10.19.710.910.910.09.78.87.2
FatigueN18841183706551513516396385
Mean51.148.250.551.051.649.748.148.0
SD10.19.69.710.710.110.89.38.3
Pain BehaviorN18511199699561507507402374
Mean50.749.047.650.052.251.350.149.7
SD10.19.710.210.610.19.79.38.7
Pain InterferenceN18561180712548499488406383
Mean51.148.347.850.151.951.649.949.7
SD10.39.39.010.211.110.99.38.7
Physical FunctionN20441363782605567565457431
Mean48.951.755.152.049.047.547.245.6
SD10.09.78.49.810.410.49.08.5
Global Mental HealthN300822061183863902873715679
Mean49.450.848.548.448.250.353.153.4
SD10.010.09.710.410.310.58.88.4
Global Physical HealthN301522121182865910875713683
Mean49.151.251.650.148.248.851.049.9
SD10.19.88.49.810.911.39.99.2