Life Opportunities Survey (LOS)Wave 2 Weighting

Andy Fallows and Sangeetha Gallagher

Overview

• Background

• Design

• W1 Weighting

• Longitudinal W2 Weighting

• Issues with weighting

Background

• Commissioned by DWP

• Follows social model of disability

• Longitudinal survey of population (possible boosts)

• Comparison of how people participate in society

Design

• Cross-sectional survey at W1• People identified as impaired at W1

interviewed face to face at W2• Sub-sample of non-impaired interviewed face

to face at W2, remainder given telephone interview

• If telephone interview identifies respondent as having gained an impairment then get face to face interview

Design

W1 Selected Sample

Design

W1 Respondents

W1 Non-Respondents

Design

Non-Impaired

Impaired

Design

Non-Impaired

Impaired

Comparison

Screening

Design

Non-Impaired

Impaired

Comparison

Screening

Design

Non-Impaired

Impaired

Comparison

Screening

Onset

Design (Complex)

Non-Impaired

Impaired

Comparison

Screening

Onset (Telephone)

Onset (F2F)

Offset

Design (Super Complex)

Non-Impaired

Impaired

Comparison

Screening

Onset (Telephone)

Onset (F2F)

Offset

Household of Comparison

Household of Impaired

Household of Onset (Telephone)

Design (Summary)

Face to Face

Telephone

W1 Weighting

• Follows standard social survey weighting

• Design weight calculated as inverse of probability of selection (taking account of multi-household adjustment)

• Non-response weight based on Output Area Classification

W1 Weighting

• Weights calibrated to Age-Sex and Region totals

• Totals obtained from ONS Demography – Census totals carried forward

• Calibration ensures that weights sum to population totals

15

Longitudinal (W2) Weighting

• Start with W1 final weight

• Create attrition weight by modelling unknown eligibility and response propensities using W1 variables and logistic regression

• Scale weights to make sure correct proportions of ineligibles are observed

• Calibrate back to W1 totals

Weight for everyone in surveyWeight-1

• Carry over the Wave 1 calibration weight as base weight

• Adjust for attrition

• Calibrate to Wave 1 population total

But......• Number of questions asked are different

Why the difference

Telephone interview Face to face interview

Screening households

Impaired person households

Control households

Onset person household

How can you compare between Wave 1 and Wave 2 if some questions are not asked in Wave 2?

Solution 1

PopulationPopulation SampleSample

Impaired Impaired including onsets

Not ImpairedControl

Screening

PopulationPopulation SampleSample

Impaired Impaired including onsets

Not Impaired Control

Keep Weight 1

Reweighted

Weighting the not impaired

• Design weight = 1/P(ctrl-hhld)

• Adjust for attrition

• Calibrate to size of wave 1 population of not impaired people = w1 population – sum(weight of w2 impaired)

Design weight for control group

AA

BB

CC

selected

Not selected

selected

Not selected

selected

Not selected

P(ctrl-hhld) = 1 – P(not selected)

Solution 1 or Weight 2

Weight 2 = design weight*attrition weight*g weightWeight 2 = Weight 1

Estimates not conforming to wave1

More exploratory work on why estimates are lower than

expected

Not Impaired at wave 2

Impaired at wave 2

Findings

Controlgroup

Telephone interview(Screening group)

Onset Not onset

Face to face interview

Onset A B C

Not Onset

D E F

Total A + D B + E C + F

B/(B+E) is biased

A/(A+D) is unbiased

C/(C+F) is unobserved

Solution 2 – Weight 3

• Give weight to people who had only a face to face interview

• Split the people who were interviewed face to face in Wave 2 but were not impaired in Wave 1 into weighting classes

• People who were identified as in onset household through telephone interview shared the weight of those who were in the same weighting class and had only face to face interview

Variables forming weighting classes

25

0

100

200

300

400

500

Age Group

Fre

qu

en

cy

11

-15

16

-30

31

-45

46

-64

65

&a

bo

ve

Continued....

26

0

200

400

600

Impairment types

Fre

qu

en

cy

Sig

ht

He

ari

ng

Lo

ng

-te

rm p

ain

Ch

ron

ic h

ea

lth c

on

diti

on

Sp

ea

kin

g

Mo

bili

ty

De

xte

rity

Bre

ath

ing

Le

arn

ing

Inte

llect

ua

l

Be

ha

vio

ura

l

Me

mo

ry

Me

nta

l he

alth

co

nd

itio

n

Oth

er

imp

air

me

nt

Weight 3

g

g g

2FtF

2 1FtF TU

baseg

ig

base calg g

i i

W

W W

2

2

1

, FtF inflow

Telephone screening inflow

baseg gicontrol

gi calg gi

WW

W

Final weight

• People who were identified as impaired in Wave 1 were weighted as

• People who had a face to face interview in Wave 2 but were not impaired in Wave 1 were weighted as

2 1 2

long cal attr g

kW W W W

2 1 2

long cal attr g

k gW W W W

THANK YOU FOR LISTENINGQUESTIONS?

THANK YOU FOR LISTENINGQUESTIONS?