# Presentation: 935417

## Data Quality of the NHIS and theContact History Instrument

**Barbara Stussman**
**Catherine Simile**
- Division of Health Interview Statistics
- National Center for Health Statistics
- Centers for Disease Control and Prevention
- Data Users Conference
- July 10, 2006

- 	The findings and conclusions in this presentation are those of the author(s) and do not necessarily represent the views of the Centers for Disease Control and Prevention.

## Purpose

- 	Describe how the implementation of CHI—the Contact History Instrument—is being used to improve the data quality of the  National Health Interview Survey

## Overview

- Non-Response:  Why do we care?
- Description of CHI
- Research Examples
- Future Directions

**Non Response:**
**Why do we Care?**

## Example Sample Composition

- 	Participating				Non-
- 	Sample					Responders

## Bias

- Nonresponse is a problem to the extent that it biases estimates
- Two components to bias:
- 	proportion of non-responders
- 	difference between non-responders and responders on     variables of interest

## Diabetes Example:Response Rate Low, No Difference, No bias

- 50% Responders, Prevalence = 10%
- 50% Non-responders, Prevalence = 10%
- True Estimate = (.50)(.10) + (.50)(.10) = 10%
- Responding Sample Estimate 	      = 10%
- No bias, regardless of the high non-response rate

## Diabetes Example:Response Rate High, Difference large, A little bias

- 97% Responders, Prevalence = 10%
- 3% Non-responders, Prevalence = 30%
- True Estimate = (.97)(.10) + (.03)(.30) = 10.6%
- Responding Sample Estimate	         = 10.0%
- 	Because the response rate is high, even though the difference in prevalence is high, the bias is small

## Slide 10

## Two Approaches to Combating Non-Response

**Interventions to reduce it**
**Knowing and living with its impact**

**Description of CHI**

## CHI Background

- 2002 Inter-Agency Nonresponse Summit
- Developed by the Census Bureau for surveys using Census as data collection agency
- Part of 2004 NHIS Redesign

## Contact History Instrument

- Allows interviewers to record information on every attempt to make contact with a household
- (whether successful or not)
- Interviewer enters information into laptop as close to time of attempt as possible
- Unique opportunity to learn about every interaction between interviewer and household

## Summary: CHI Instrument

- Data on approximately 200,000 Visit attempts
- Collects information per attempt on:
- Mode of contact attempt
- Contact or noncontact
-  Outcome of attempt (complete, partial, unable to conduct interview)
- Concerns/Reluctance
- Strategies attempted

**Examples of CHI Research**

## Research Topics

- Optimal Call Times
- Interviewer Strategies

## Optimal Call Times

- What is the optimal time for making a contact attempt?
- When are interviewers making attempts?
- Does time of first contact influence outcome?
- Are interviewers making attempts at optimal times?

## Slide 25

## More Results: Optimal Times

- More first attempts occur on weekday afternoons; shift to weekends and evenings on second and later attempts
- Weekday evenings and weekends best time for making first contact
- Weekday afternoon first contacts more likely to result in complete interview than weekday evening first contacts

## Interviewers Strategies

- What strategies are interviewers using and in what combination?
- In what ways do interviewers shift strategies with different field situations?
- How is the use of certain strategies related to gaining contact and/or cooperation?

## Strategies Used on 1st, 2nd, 3rd Attempts

## Number of Strategies Used per Attempt

**Knowing and Living with the Impact of Non-Response**

## Sample Composition

- 	More Willing			High		Non-
- 	Responders			Effort	Respon-
- 						Respon-	ders
- 						ders
- ___________________________________

## Defining High Effort Responders

- 	**Definition 1:  Cooperation**
- 	Field Representative indicated at least one time in the contact history of the case that the case could be a potential refusal.
- 	**Definition 2: Contactability**
- 	Field Representative attempted to contact a household at least 4 times before making contact with a member of the household.

## Sample Health Indicators

**Reported Diagnosed Conditions**
- Diabetes
- Hypertension
- Arthritis

## 

	How different are High Effort Responders from Lower Effort Responders on Selected Health Indicators?

- 	**How different are High Effort Responders from Lower Effort Responders on Selected Health Indicators?**

## Diagnosed Conditions

|  | 
TOTAL | Pot. Refusal |  | 4+ Noncontact |  |
| --- | --- | --- | --- | --- | --- |
|  |  | HE | NHE | HE | NHE |
| Diabetes

Hypertension

Arthritis
 | 7.03

25.38

21.67 | 6.62

22.08*

20.70 | 7.05

25.47*

21.70 | 5.17**

19.37**

16.46** | 7.13**

25.70**

21.96** |

- 		**To what degree are the ****	****national health estimates **
**	****	****biased? **

## Estimating Diagnosed Conditions

|  | All Cases | Without Refusal Cases | Without Noncontact
Cases |
| --- | --- | --- | --- |
| Diabetes

Hypertension

Arthritis
 | 6.9

25.1

21.5 | 7.0***

25.3***

21.6** | 7.0**

25.3***

21.6 |

## Bias summary

- There are significant and substantive differences between high and low effort groups
- Though there is a small effect on the national estimates, should the proportion of the high effort grow, we would expect a greater impact
- These estimates are at the national level and do not speak to subgroup analyses

## Future Directions

- CHI has been a valuable tool for learning about data quality
- Our goal is to use this research to make specific field recommendations we hope will lead to an increase in response rates
- Use it to continue to produce high quality health estimates

## Contact Information

- Barbara Stussman
- Catherine  M.  Simile
- National Center for Health Statistics
- Division of Health Interview Statistics
- 3311 Toledo Road, Room 2115
- Hyattsville, MD 20782
- Barbara, (301) 458-4529
- Catherine, (301) 458-4499
- Email: bstussman@cdc.gov; csimile@cdc.gov