Table 1 Realisation of recommendations for increasing the response rate

Envelope

Logo

√

P

Postage stamp (if N is small)

Large N

P

Address personally

√

Cover letter

T

Reliable letter-head/letter-head of the university

√

P

Personal form of address

√

Explanation of aims of the study

√

Information about researchers

On demand

T

Ensure anonymity

√

Name of the researchers/institution

√

Telephone number

√

Office hours of the researchers

X

P

Hand-written signature

√

Not longer than 1 page

√

Clarify importance of participation

√

Brief information about results

On demand

Questionnaire

A4, white, tacked

√

C

Short, not more than 16 pages

√

T

Easily readable and understandable/blocks of questions

√

No sociodemographic/precarious questions at the beginning

√

Preferably closed response format

√

Preferably no filter questions

√

Consider rules to formulate questions (e.g. no double negative)

√

Front page: title, institution, address, contact

√

Directions on how to fill in the questionnaire

X

At the end: 1/2 page for comments

¹/₄ page

Privacy policy

How are data handled?

X

Ensure anonymity

√

Ensure no disclosure of data

X

Data protection officer involved

√

Envelope for reply

Return free of charge

√

Announcement

C

Only if no intensive follow-up

√

Salience

T

Interesting topic

√

Follow-up

F

First dispatch, thank-you note/reminder, second dispatch of questionnaire

√

Recognised authorities

Here: newspaper article, cover letter of National Medical Council

√

Material incentives

C

Monetary: no delayed incentives

Delayed fixed amount

C

Non-monetary (e.g. brochure)

X