Survey Sampling

A description of the sampling methodologies used on the Departing Passenger Surveys

CAA surveys generally operate for twelve month periods with anywhere from  3,000 to 70,000 interviews being achieved, depending on airport size.  The surveys usually follow a stratified sampling design (stratified by carrier, route and quarter), with interviews taking place in the gaterooms.  The interviews are then weighted to actual traffic levels.  (Less often, a random sample is obtained by interviewing at points in the lounge - in this instance a further level of weighting is required to account for the sampling proportion obtained during the shift). 

Surveys usually run on an annual basis, with shifts spread as evenly as practical throughout the year.  A record of the flights sampled is regularly monitored to ensure that where possible all routes, and in most cases all flight numbers, are covered regularly.

Departing passengers are selected for interview using a strict sampling system.  Interviews are weighted to the two-way passenger flow, under the assumption that over the period, departing and arriving passengers will show the same characteristics.  Information is collected from passengers by a skilled interviewing fieldforce.

An interview usually lasts 5 - 7 minutes, and involves around 30 questions being asked. All passengers are eligible, apart from children under two years of age.

It is assumed that passengers who are chosen for interview, but are unwilling or unable to respond (e.g. because of time constraints) have the same characteristics as those who are successfully interviewed.  Thus no adjustments are made for non-response, either by item or by questionnaire.

The notes below outline the sampling methodology that is used when interviewing in the gateroom.  This method can be used irrespective of the number of team members present and ensures that a random selection of passengers are selected for interview.

  1. The interviewing area where passengers are sampled should be clearly defined to all team members present.
  2. The interviewing area is divided into a number of virtual areas, dependent upon the number of team members available to interview. If there are four team members, the interviewing area should be divided into quarters, where there are only three team members, then the area should be divided into thirds and so on.
  3. Each interviewer is assigned an area. It will then be that interviewer's responsibility to sample passengers who move into their area.
  4. It is of key importance that interviewers do not avoid certain passengers or show any favouritism to other groups of passengers.
  5. On selecting the first passenger (perhaps to the extreme left of the interviewing area) the interviewer will run through the questionnaire in the normal manner. On the completion of this interview, the interviewer will then count three more passengers (in this example, towards the right). The third passenger counted, assuming that they are eligible for interview will then be interviewed. Once this interview has been completed, the interviewer will then count a further three passengers and begin the process again.  The same passenger cannot be interviewed twice.
  6. The interviewing areas can be redefined during busy or quiet periods in line with the number of team members available to work. 

 

The list below shows the airports we have surveyed in recent years. 

ABERDEEN

Aberdeen was last surveyed in 2009 and prior to this in 2005, 2001, 1996 and 1990. 

BELFAST CITY

Belfast City was last surveyed in 2006 and prior to this in 2001 and 1994/95. 

BELFAST INTERNATIONAL

Belfast International was last surveyed in 2006 and prior to this in 2001 and 1994/95. 

BIRMINGHAM

Birmingham is being surveyed in 2010 and prior to this in 2006, 2003, 1999, 1996 and 1992/93. 

BRISTOL

Bristol was last surveyed in 2008 and prior to this in 2003, 2000 and 1994/95.

BOURNEMOUTH

Bournemouth was last surveyed in 2008/09 and prior to this in 2005 and 2000. 

CARDIFF

Cardiff was last surveyed in 2008 and prior to this in 2003, 2000 and 1994/95.

DONCASTER

Doncaster was last surveyed in 2007.  This was the first survey at the airport.

DURHAM TEES VALLEY

Durham Tees Valley was last surveyed in 2009 and prior to this in 2005, 1999 and 1994/95. 

EDINBURGH

Edinburgh was last surveyed in 2009 and prior to this in 2005, 2001, 1996 and 1990. 

EXETER

Exeter was last surveyed in 2008 and prior to this in 2003, 2000 and 1994/95.

GLASGOW

Glasgow was last surveyed in 2009 and prior to this in 2005, 2001, 1996 and 1990. 

HUMBERSIDE

Humberside was last surveyed in 2007 and prior to this in 1999 and 1994/95. 

INVERNESS

Inverness was last surveyed in 2009 and prior to this in 2005, 2001, 1996 and 1990. 

LEEDS BRADFORD

Leeds Bradford is being surveyed in 2010 and prior to this in 2005, 1999 and 1994/95. 

LIVERPOOL

Liverpool is being surveyed in 2010, and prior to this in 2003 and 1999.

LONDONDERRY

Londonderry was last surveyed in 2006.

LONDON CITY

London City is being surveyed in 2010 and prior to this in 2005, 2003, 2000, 1996 and 1991.

LONDON GATWICK

Gatwick has been surveyed continuously since 1997.  Prior to this Gatwick was surveyed in 1996, 1991 and 1987. 

LONDON HEATHROW

Heathrow has been surveyed continuously since 1997.  Prior to this Heathrow was surveyed in 1996, 1991 and 1987. 

LONDON LUTON

Luton has been surveyed continuously since 2001.  Prior to this it was surveyed in 2000, 1996, 1991 and 1987. 

LONDON STANSTED

Stansted has been surveyed continuously since 2001.   Prior to this it was surveyed in 2000, 1996, 1991 and 1987. 

MANCHESTER

Manchester has been surveyed continuously since 1997.  Prior to this Manchester was surveyed in 1996, 1992/93 and 1987. 

NEWCASTLE

Newcastle was last surveyed in 2005.  Prior to this it was surveyed in 2001, 1999 and 1994/95. 

NORWICH

Norwich was last surveyed in 1999 and prior to this in 1994/95. 

NOTTINGHAM EAST MIDLANDS

Nottingham East Midlands was last surveyed in 2006 and prior to this in 2003, 1999 and 1992/93.

PRESTWICK

Prestwick was last surveyed in 2009 and prior to this in 2005. 

SOUTHAMPTON

Southampton was last surveyed in 2000 and prior to this in 1994/95.