A general procedure for conducting laboratory and field experiments has been described in this chapter. Some experiments required slight variations in procedure and equipment; these are explained in each relevant chapter. These methods, equipment and procedures will be used to investigate thermal comfort on train journeys.
PART 2 – LABORATORY EXPERIMENTS
3 A methodological investigation examining the optimum
methods of data collection on train journeys
3.1 Summary
Before experiments measuring thermal comfort can take place, an appropriate data collection method is required. This chapter describes a laboratory experiment conducted to determine an optimum method for collecting subjective thermal comfort information on a train journey. The experiment took place between February and May 2007.
18 participants (9 males, 9 females) attended the laboratory on three occasions using a different data collection method each time. The three methods used during the study were: (1) Paper questionnaire, (2) Personal Digital Assistant (PDA) and (3) Voice recorder. Methods 2 and 3 were compared against the paper questionnaire as this has been the predominant method of applying subjective data gathering in prior research and can be considered the benchmark for comparison.
Each participant spent an hour in the thermal chamber and was asked to report on thermal comfort immediately on entering and at 15 minute intervals. At the end of the study participants were asked to compare the methods using a number of criteria.
The experiment determined that participants scored equally when using each of the methods and there was no difference between them. Participants stated that they would prefer to use the PDA on a train journey as it would give them more privacy than the other two methods, in addition to allowing them to blend in with other rail users. The voice recorder was the least favoured method for use on a train journey; due to the topics under discussion and the perception that other train users would be able to overhear recordings.
3.2 Introduction
Traditionally, measurement of subjective thermal comfort has been carried out using paper- based questionnaires (Underwood and Parsons 2005, McIntyre and Griffiths 1975, Griffiths and McIntyre 1974, Arens et al. 2006, Hodder 2002, Stennings 2007). However, the paper method may not be suitable under certain journey conditions (e.g. inclement weather, when standing on a platform or getting on and off the train) and alternative methods of data collection were examined.
Personal Digital Assistants (PDAs) have been increasingly used in research to acquire subjective information (Bernhardt et al. 2007, Dale and LeFlore 2007, Jamison et al. 2001, Raymond and Ross 2000, Trapl et al. 2005) They may be more appropriate for use on trains as there are less cumbersome than the paper equivalent. They can also significantly reduce transcription time. In addition, missing data can be eliminated and entries can be time and date stamped enabling detection of entries completed retrospectively. Thus a more complete picture of the data can be produced.
Verbal reports have also been used in research (Ericsson and Simon 1980, Bainbridge and Sanderson 2005, Ryan and Haslegrave 2007b) as they can provide a rich data source as well as extending the potential experimental population to those with limited reading and writing skills. Verbal reports are also a way of capturing subjective responses when paper-based or PDA systems are impractical to use such as when walking. Voice recorders are the easiest method of collecting verbal reports as they do not require an observer to write down responses.
The experiment described in this chapter aimed to determine whether PDAs and voice recorders are suitable for collecting thermal comfort information on train journeys. They were compared with the existing paper-based method to establish their accuracy and ease of use. The experiment was also designed to establish which method would be most preferred by participants‘ for use on lone train journeys i.e. when an experimenter is not present. Genders were compared to determine if method preference and responses differed between males and females.
3.2.1 Preliminary investigations
Prior to conducting the experiment comparing the three methods, initial investigations were made to determine suitable and meaningful questions to ask about a person‘s train journey. Considerations were made for all journey parts (home, travelling, on the platform and train) and the aspects of each that could affect thermal comfort. In addition to this, standard questions
regarding thermal comfort were also asked (subjective scales of: Sensation, Comfort, Stickiness, Draught, Preference, and Pleasantness, see Figure 3.1).
Four questionnaire users were required to use the scales and enter appropriate scores in a table provided (see Figure 3.2); the whole questionnaire can be found in Appendix C. The questionnaire was formed into a paper booklet and tested on three train journeys to establish its effectiveness in determining thermal comfort levels. From these preliminary tests it was noted that paper may not be the optimum method for obtaining this information. The method was unsuitable in wet or windy weather conditions on station platforms and required a hard surface to write on. Alternative methods of data collection were therefore examined.
3.2.2 Experiment aims and objectives
The aim of this experiment was to determine the optimum method for the collection of subjective thermal comfort data on train journeys. An additional aim was to determine the methodological implications of collecting data in a field environment by simulating conditions in the laboratory.
Experimental objectives:
1. To compare different data collection methods and determine whether they can be used interchangeably – this will be accomplished by comparing subjective votes across each method and by comparing results with an existing index of thermal comfort;
2. To determine which method is most preferred by participants for use on train journeys – this will be accomplished by asking participants to rate each method on its ease of use and their preference;
3. To determine if there are differences between male and female subjective scores when using each method – subjective scores will be compared to determine if there are differences between the methods.