Introduction

A pilot experiment, also called a pilot study, is a small scale

preliminary study conducted before the main research, in order

to check the feasibility or to improve the design of the

research. A pilot, or feasibility study, is a small experiment

designed to test logistics and gather information prior to a

larger study, in order to improve the latter’s quality and

efficiency.

Pilot studies, therefore, may not be appropriate for case

studies. They are frequently carried out before large-scale

quantitative research, in an attempt to avoid time and money

being wasted on an inadequately designed project. A pilot

study is usually carried out on members of the relevant

population, but not on those who will form part of the final

sample. This is because it may influence the later behaviour of

research subjects if they have already been involved in the

research.

A pilot experiment is often used to test the design of the full-

scale experiment which then can be adjusted, a potentially

valuable insight. Should anything be missing in the pilot, it can

be added to the experiment to improve chances of a clear

outcome that will influence the full-scale (and more expensive)

experiment.

Often in engineering applications, pilot experiments are used to

sell a product and provide quantitative proof that the system

has potential to succeed on a full scale basis. Pilot experiments 1

are also used to reduce cost, as they are less expensive than

full experiments. If there is not enough reason to provide full

scale applications, pilots can generally provide this proof.

In sociology, pilot studies can be referred to as small-scale

studies that will help identify design issues before the main

research is done.

The term pilot study is used in two different ways in social

science research. It can refer to so-called feasibility studies

which are "small scale version[s], or trial run[s], done in

preparation for the major study"). However, a pilot study can

also be the pre-testing or 'trying out' of a particular research

instrument (Baker 1994: 182-3). One of the advantages of

conducting a pilot study is that it might give advance warning

about where the main research project could fail, where

research protocols may not be followed, or whether proposed

methods or instruments are inappropriate or too complicated.

These are important reasons for undertaking a pilot study, but

there are additional reasons, for example convincing funding

bodies that your research proposal for the main study is worth

funding. Thus pilot studies are conducted for a range of

different reasons.

Although pilot experiments have a well-established tradition in

public action, their usefulness as a strategy for change has

been questioned, at least in the domain of environmental

management. It is argued that extrapolation from a pilot study

to large scale environmental strategy cannot be assumed to be

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possible, partly due to the exceptional resources and

favourable conditions that often accompanies a pilot study.

Reasons for Pilot Studies

A pilot study can reveal deficiencies in the design of a proposed

experiment or procedure and these can then be addressed

before time and resources are expended on large scale studies.

Animal experiments are not usually carried out in isolation, but

are part of a programme of research. A good research strategy

requires careful planning and a pilot study will often be a part

of this strategy.

A pilot study is normally small in comparison with the main

experiment and therefore can provide only limited information

on the sources and magnitude of variation of response

measures. It is unlikely, for example, that a pilot study alone

can provide adequate data on variability for a power analysis to

estimate the number of animals to include in a well designed

experiment. A systematic review of the literature or even a

single publication is a more appropriate source of information

on variability. The pilot study may, however, provide vital

information on the severity of proposed procedures or

treatments.

Other reasons include:

Developing and testing adequacy of research instruments

Assessing the feasibility of a (full-scale) study/survey

Designing a research protocol

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Assessing whether the research protocol is realistic and

workable

Establishing whether the sampling frame and technique

are effective

Assessing the likely success of proposed recruitment

approaches

Identifying logistical problems which might occur using

proposed methods

Estimating variability in outcomes to help determining

sample size

Collecting preliminary data

Determining what resources (finance, staff) are needed for

a planned study

Assessing the proposed data analysis techniques to

uncover potential problems

Developing a research question and research plan

Training a researcher in as many elements of the research

process as possible

Convincing funding bodies that the research team is

competent and knowledgeable

Convincing funding bodies that the main study is feasible

and worth funding

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Convincing other stakeholders that the main study is

worth supporting

Logistical issues which may be revealed by a pilot study

A pilot study may address a number of logistical issues. As part

of the research strategy the following factors can be resolved

prior to the main study:

• Check that the instructions given to investigators (e.g.

randomisation procedures) are comprehensible;

• Check that investigators and technicians are sufficiently

skilled in the procedures;

• Check the correct operation of equipment;

• Check that the experimental animal can perform a task

(physical or cognitive)

• Check the reliability and validity of results

• Detect a floor or ceiling effect (e.g. if a task is too difficult or

too easy there will be skewed results)

• Assess whether the level of intervention is appropriate (e.g.

the dose of a drug);

• Identify adverse effects (pain, suffering, distress or lasting

harm) caused by the procedure, and the effectiveness of

actions to reduce them (e.g. analgesia dose rate and schedule);

• Define early humane endpoints.

What to do with the Data / Information5

The information obtained on logistical issues should be

incorporated into the main study design. As the purpose of a

pilot study is to assess the feasibility of an experiment it is very

rarely sensible to present more than summary statistics of the

data. In fact, the data might be irrelevant if problems with the

methods are discovered.

If a pilot study does not lead to modification of materials or

procedures then the data might be suitable for incorporation

into the main study. The sampling strategy used to select

subjects, and the possibility of changes over time should be

carefully considered before incorporating pilot data. Even if the

pilot data are not used in this way, and even if the final design

differs markedly from the pilot, it is useful to include

information on the pilot study in any publications or reports

arising from the main experiment as this can inform the design

of future experiments.

It may be necessary to carry out a second pilot study to assess

the revised main study or in some cases the main study may

have to be abandoned.

Before beginning such a full research project, researchers need

to know that their study is valid and the study’s design will be

able to capture the data they are looking for. They need to

know that the research they plan to do will be the most

accurate and reliable research possible. The best way to do this

is to perform a pilot study.

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Think of a pilot study as a miniature study. Typically, it will call

for fewer literary resources, a shorter time frame, and fewer

research subjects. For example, if the full study is going to

reference 50 previous books or articles, the pilot study might

reference five or ten. If the full study will call for a survey of

100 people, the pilot study might rely on surveying a small

handful of individuals. If the full study is going to take many

months or years to complete, the pilot study can focus on two

or three lakes over the course of a few weeks.

Methods and Statistics Required For a Pilot Study

The researcher has many options. This research method could

be as simple as using interview guides, and the measurement

techniques used could be as simple as using averages, simple

percentages, and standard deviations. However, the

researchers may wish to employ more sophisticated methods

and analyses and may use Appendix A as a basic guide.

A small chemistry experiment in a college laboratory, for

example, costs very little, and mistakes or validity problems

easily rectified. At the other end of the scale, a medical

experiment taking samples from thousands of people from

across the world is expensive, often running into the millions of

dollars.

Finding out that there was a problem with the equipment or

with the statistics used is unacceptable, and there will be dire

consequences.

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A field research project in the Amazon Basin costs a lot of time

and money, so finding out that the electronics used do not

function in the humid and warm conditions is too late.

To test the feasibility, equipment and methods, researchers will

often use a pilot study, a small-scale rehearsal of the larger

research design. Generally, the pilot study technique

specifically refers to a smaller scale version of the experiment,

although equipment tests are an increasingly important part of

this sub-group of experiments.

For example, the medical researchers may conduct a smaller

survey upon a hundred people, to check that the protocols are

fine.

The Amazon Researchers may perform an experiment, in

similar conditions, sending a small team either to the Amazon

to test the procedures, or by using something like the tropical

bio-dome at the Eden Project.

Pilot studies are also excellent for training inexperienced

researchers, allowing them to make mistakes without fear of

losing their job or failing the assignment.

Logistical and financial estimates can be extrapolated from the

pilot study, and the research question, and the project can be

streamlined to reduce wastage of resources and time.

Pilots can be an important part of attracting grants for research

as the results can be placed before the funding body.

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Generally, most funding bodies see research as an investment,

so are not going to dole out money unless they are certain that

there is a chance of a financial return.

Unfortunately, and paper reporting the preliminary pilot study,

especially if problems were reported, is often stigmatized and

sidelined. This is unfair, and punishes researchers for being

methodical, so these attitudes are under a period of re-

evaluation.

Discouraging researchers from reporting methodological errors,

as found in pilot studies, means that later researchers may

make the same mistakes.

The other major problem is deciding whether the results from

the pilot study can be included in the final results and analysis,

a procedure that varies wildly between disciplines.

Pilots are rapidly becoming an essential pre-cursor to many

research projects, especially when universities are constantly

striving to reduce costs. Whilst there are weaknesses, they are

extremely useful for driving procedures in an age increasingly

dominated by technology, much of it untested under field

conditions.

Methods of Pilot Studies

Pilot studies can be based on quantitative and/or qualitative

methods and large-scale studies might employ a number of

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pilot studies before the main survey is conducted. Thus

researchers may start with "qualitative data collection and

analysis on a relatively unexplored topic, using the results to

design a subsequent quantitative phase of the study"

(Tashakkori & Teddlie 1998: 47). The first phase of a pilot might

involve using in-depth interviews or focus groups to establish

the issues to be addressed in a large-scale questionnaire

survey. Next the questionnaire, e.g. the wording and the order

of the questions, or the range of answers on multiple-choice

questions, might be piloted. A final pilot could be conducted to

test the research process, e.g. the different ways of distributing

and collecting the questionnaires. For example, a recent study

exploring nurses' and midwives' attitudes to research followed

this pattern. In this study focus groups were used to identify

key issues from which a questionnaire could be developed, and

this was then piloted prior to the study proper (Hundley et al.

2000). On a much larger scale, the largest (decennial) survey in

the UK, the Census (of 29th April 2001), tested methodological

and other changes to the 1991 Census questionnaire on over

100,000 households in 1997. This 1997 Census Test "provided

essential information on public reaction to new questions and

form style as well as assessing the success of collection and

processing methods" (Office for National Statistics, General

Register Office for Scotland, Northern Ireland Statistical &

Research Agency 1999: 15).

Pilot studies may also try to identify potential practical

problems in following the research procedure. For example, in a

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recent Scottish study of maternity care the pilot phase

demonstrated that the proposed means of distributing the

questionnaires would not be adhered to (van Teijlingen et al.

2001). Without consulting the research team, the person

responsible for distributing the questionnaires from the hospital

records department decided that it was better to distribute

them through the community midwives. This was despite the

fact that the hospital itself had suggested the records

department as a means of distribution. Other problems such as

poor recording and response rates can also be identified and

precautionary procedures or safety nets can be devised.

The steps used to pilot a questionnaire on a small group of

volunteers, who are as similar as possible to the target

population, are listed in Table 2. Pilot studies can also uncover

local politics or problems that may affect the research process.

In the study described above, the managers of maternity

services had different perceptions of what the forthcoming

changes in the Data Protection Act (1998) allowed them to do

about the involvement of their clients in research. In the above

mentioned recent Scottish study of maternity care one head of

midwifery voiced ethical concerns about the use of follow-up or

reminder letters due to a previous local incident, where parents

of an ill baby had been sent a questionnaire which was felt to

be inappropriate, and as a result of changes to the UK Data

Protection Act. Consequently reminders were sent out via the

head of midwifery in case there were any problems with the

newborn baby.

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Problems of Pilot Studies

It should be recognised pilot studies may also have a number of

limitations. These include the possibility of making inaccurate

predictions or assumptions on the basis of pilot data; problems

arising from contamination; and problems related to funding.

These issues are now discussed in turn.

Completing a pilot study successfully is not a guarantee of the

success of the full-scale survey. Although pilot study findings

may offer some indication of the likely size of the response rate

in the main survey, they cannot guarantee this because they do

not have a statistical foundation and are nearly always based

on small numbers. Furthermore, other problems or headaches

may not become obvious until the larger scale study is

conducted.

A further concern is that of contamination. This may arise in

two ways:

1. where data from the pilot study are included in the main

results;

2. where pilot participants are included in the main study,

but new data are collected from these people.

Social scientists engaged in predominantly quantitative

research are likely to argue that: "an essential feature of a pilot

study is that the data are not used to test a hypothesis or

included with data from the actual study when the results are

reported" (Peat et al. 2002: 57). The obvious concern is that if

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there were problems with the research tool and modifications

had to be made in the light of the findings from the pilot study,

data could be flawed or inaccurate. However, where an

established and validated tool is being used and the pilot study

is determining other methodological aspects such as

recruitment rates, it could be argued that such data may be of

value.

A more common problem is deciding whether to include pilot

study participants or site(s) in the main study. Here the concern

is that they have already been exposed to an intervention and,

therefore, may respond differently from those who have not

previously experienced it. This may be positive, for example

the participants may become more adept at using a new tool or

procedure. However it may also be negative with participants

showing a decline in following a protocol because it is no longer

novel. Indeed both changes in behaviour have long been

recognised and a 'run in' period, where an intervention is

introduced prior to a study, is often used for these reasons. The

concern about including participants from the pilot study in the

main study arises because only those involved in the pilot, and

not the whole group, will have had the experience. In some

cases however it is simply not possible to exclude these pilot-

study participants because to do so would result in too small a

sample in the main study. This problem arises in particular

where the samples are clusters, for example schools, prisons or

hospitals. In such cases one can conduct a sensitivity analysis

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(or sub-group analysis) to assess to what extent the process of

piloting influences the size of the intervention effect.

Contamination is less of a concern in qualitative research,

where researchers often use some or all of their pilot data as

part of the main study. Qualitative data collection and analysis

is often progressive, in that a second or subsequent interview

in a series should be 'better' than the previous one as the

interviewer may have gained insights from previous interviews

which are used to improve interview schedules and specific

questions. Some have therefore argued that in qualitative

approaches separate pilot studies are not necessary (e.g.

Holloway 1997: 121). For example, a qualitative interviewer

conducting 15 focus group interviews will listen to the

recordings or read through the transcripts of the first three or

four in order to improve the questions, the way of introducing

the issues into the group interview or even to add new topics.

Thus, although there is no specific pilot study, analysis of the

earlier focus groups may help improve the later ones. However,

Frankland and Bloor (1999: 154) argue that piloting provides

the qualitative researcher with a "clear definition of the focus of

the study" which in turn helps the researcher to concentrate

data collection on a narrow spectrum of projected analytical

topics. Piloting of qualitative approaches can also be carried out

if "the researcher lacks confidence or is a novice, particularly

when using the interview technique" (Holloway 1997: 121).

Problems may also arise where a pilot study requires a

significant investment of resources, making it difficult for the 14

study team to call a halt to the research after an unsuccessful

pilot study. Researchers might be tempted to make

considerable changes in the main study, rather than deciding

that the proposed study is not possible with the available

resources, time, population, etc. In contrast, funding bodies

may be reluctant to fund a further study if the pilot has been

substantial as they may view the research as no longer original,

especially if results from the pilot study are published.

Why are Pilot Studies Not Reported?

Publication bias may occur because of a tendency for journals

to accept only papers that have statistically significant results

and not to report non-significant effects (Mahoney 1977; Chann

1982; Dickersin, 1990). A recent study exploring research on

passive smoking found a difference of two years in the median

time to publication between findings from significant and non-

significant studies (Misakian & Bero 1998). It follows that

papers reporting methodological issues, such as those

identified during the pilot phase of a study, will also be less

attractive to publishers.

Selective publication of research results has been recognised

as a problem. It may lead to an overestimation of the

effectiveness of interventions, exposing patients to useless or

harmful treatments, while overestimation of adverse effects

may mean that patients are denied effective forms of care

(Oxman et al. 1994). In the past editors have recognised the 15

dangers of publication bias with respect to clinical trials and

have offered 'an amnesty for unpublished trials' in an attempt

to overcome these problems (Smith & Roberts, 1997).

However, it is equally important to ensure that lessons learned

with respect to the research method are shared, otherwise

patients may be subjected to poorly developed tools or money

may be wasted because methods of recruitment failed. A

consistent selection bias favouring reports of primary research

over papers on research methods, theoretical thinking, or

secondary analysis, can lead to many of researchers re-

inventing the wheel without having had the opportunity to learn

from other people's experience.

Conclusions

It has been said that pilot studies are likely to be

"underdiscussed, underused and underreported" (Prescott and

Soeken, 1989 p60). Full reports of pilot studies are rare in the

research literature (Lindquist, 1991; Muoio et al, 1995, van

Teijlingen et al. 2001). When reported, they often only justify

the research methods or particular research tool used. Too

often research papers only refer to one element of the pilot

study, for example, to the 'pre-testing' or 'pilot testing' of a

questionnaire (De Vaus, 1993). Such papers simply state: "the

questionnaire was tested for validity and reliability." When pilot

studies are mentioned in more detail in academic papers and

reports, researchers regularly comment that they "had learned

from the pilot study" and made the necessary changes, without

offering the reader details about what exactly was learnt. Some 16

of these processes and outcomes from both successful and

failed pilot studies might be very useful to others embarking on

projects using similar methods and instruments. This is

particularly important because pilot studies can be "time-

consuming, frustrating, and fraught with unanticipated

problems, but it is better to deal with them before investing a

great deal of time, money, and effort in the full study" (Mason

and Zuercher, 1995). It has also been argued that the current

research climate demands accountability from researchers,

which means that there is a need to ensure the best possible

use of research results (Crosswaite and Curtice 1994). We

would like to go one step further and argue that researchers

have an ethical obligation to make the best use of their

research experience by reporting issues arising from all parts of

a study, including the pilot phase. Well-designed and well-

conducted pilot studies can inform us about the best research

process and occasionally about likely outcomes. Therefore

investigators should be encouraged to report their pilot studies,

and in particular to report in more detail the actual

improvements made to the study design and the research

process.

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