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Year : 2015  |  Volume : 16  |  Issue : 2  |  Page : 57-60

Research instruments

Professor, College of Nursing, CMC, Vellore, India

Date of Web Publication23-May-2020

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The research instruments are the tools that the researcher uses to collect data. There are different types of instruments based on the structure or format, purpose, nature, and availability. The common types of instruments used in the nursing studies are questionnaires and scales. Instruments are selected based on the research question. The selection of instrument is a very important part of the research process and is lengthy and involving various steps. The credibility of an instrument depends on the validity and reliability. Whether, standardized or developed by the researcher, the validity and reliability has to be established before it is used.

Keywords: research instrument, validity, reliability

How to cite this article:
Sathiyaseelan M. Research instruments. Indian J Cont Nsg Edn 2015;16:57-60

How to cite this URL:
Sathiyaseelan M. Research instruments. Indian J Cont Nsg Edn [serial online] 2015 [cited 2022 Dec 1];16:57-60. Available from: https://www.ijcne.org/text.asp?2015/16/2/57/284862

  Introduction Top

Instrument is the generic term that researchers use for a measurement device e.g., questionnaires, checklists. The selection of a research instrument is a very crucial step in the research process. It is used to measure the study variables. An extensive literature search will help the researcher to identify the appropriate instrument to be used. The type of research instrument is decided based on reviewing the data needs. A research instrument should capture each variable in terms of its conceptual or theoretical definition (Polit & Beck, 2012).

  Classification Top

The research instruments can be classified based on the structure, purpose, nature, and availability of the instrument (see [Figure 1]).
Figure 1: Classification of research instrument

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According to the structure or format, the instrument is further classified as questionnaires and scales. These are commonly used instruments in nursing research (Burns, & Grove, 2011).

  1. Questionnaires Top

Questionnaires are the most frequently used instrument to collect data. It helps to gather data concerning knowledge, attitudes, opinions, facts etc. It can be open- ended or closed-ended questions. The open-ended questions allow the subjects give spontaneous opinions. In this type, the researcher has less control over subjects’ answers. Closed- ended questions allow subjects to select an answer from among several choices. The questions should be constructed using simple language and should signify one idea e.g., To assess the annual income of a subject, an open-ended question can be framed in the following way:

What is your family’s average income during the last year? On the other hand, the same question can also be closed ended.

What was your family’s average income during the last year?

  1. less than 1000/-
  2. 1001 - 5000/-
  3. 5001 - 10,000/-
  4. More than 10,000/

  2. Scales Top

Scales ask the respondents to rank some trait or ability on a continuum of possible responses. The common types of scales are Likert scale, Guttman scale, and Visual Analog Scale (VAS). Likert scales require subjects to respond to a series of statements to express a view point. Guttman scale is composed of set of items that are arranged in an order, so that an individual who agrees with a particular item also agrees with items of lower order. Visual analog scales are used to measure the subjective phenomena. An example for Likert scale is given below:

Ms. K, an engineering graduate wanted to investigate job satisfaction of IT professionals. Hence, she used a self-reported scale to collect data. One of the items in that scale is

An example for a Guttmann scale would be as follows:

  • Nursing process ensures to identify perceived needs of patients
  • Nursing process helps to identify actual and potential problems of patients
  • Nursing process aids in prioritizing the care of the patients
  • Nursing process helps to maintain quality while delivering care
  • Nursing students should be empowered to use nursing process approach

[Figure 2] is an example of a Visual Analogue Scale. Mr. M, a critical care nurse wanted to study the fear in adults using a visual analogue scale projected below
Figure 2: Visual analogue scale for fear

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The types of research instrument based on the purpose are classified into cognitive, affective, and psychomotor research instruments which is outlined in [Figure 3] with examples. The cognitive research instruments are used to measure the academic achievements of the subjects. The affective research instruments are used to assess the feelings, values, and attitudes towards self and others. The psychomotor research instruments are used to assess the subject’s feelings and thoughts to an ambiguous stimulus (Brink & Wood, 1989; Richard, 2013).
Figure 3: Classification of research instrument based on the purpose

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According to the nature of the instrument used for data collection, it is grouped into researcher-completed instruments and subject-completed instruments, distinguished by those instruments that researchers administer versus those that are completed by participants. Data collection tools used by the researcher and the subject are listed in [Table 1]. The research question determines the type of instrument to be used for collecting data (Lincoln & Guba, 1985).
Table 1: Data Collection Tools Used by the Researcher and the Subject

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Research instruments are also classified as standardized tools and researcher-developed tools (LoBiondo-Wood & Haber, 2014).

1. Standardized tools: Standardized tools are those which are already developed and validated by researchers being used for studies according to the need. Some tools are freely available especially for learners in research and for those projects which does not involve generation of income or have any business motive. It is available for the development of knowledge and evidence for further practice in the profession. However, the researcher has to obtain permission from the author of the instrument or give appropriate credit to the author e.g., Ms. M wanted to investigate anxiety among primary care givers of patients with bipolar disorder. Hence she used Hamilton Anxiety Rating Scale (1959), which is a standardized research tool.

2. Researcher-developed tools: The researcher develops an instrument based on the specific need of the study. Instrument development is complex and time consuming. It involves defining the concept to be measured, clarifying the target population, developing the items, assessing the items for content validity, develop instructions for respondents and users, pretest and pilot the test items, and estimating reliability and validity e.g., Mr. K, a psychiatric nurse wanted to assess perception of patients who are under restraints. He developed a tool, which was content validated by the faculty in the department of psychiatric nursing and pretested for its reliability, which was statistically estimated to be .81.

  Selection of research instrument Top

The type of research instrument determines the data collection methods. The most common measurement methods used in nursing research are physiological measurement, observational measurement, interviews, questionnaires, and scales. The selection of a suitable instrument is of vital importance for a successful research. An appropriate instrument is useful to measure or collect complete data related to the research question. One or more tools may be used in combination depending on the purpose of the study. The following questions can be addressed by the researcher to determine the best instrument for measuring the study variables (Burns & Grove, 2011; Tools of Research, 2015).

  • Does the instrument measure what the researcher wants to measure?
  • Does the instrument reflect the conceptual definition of the variable?
  • Is the readability level of the instrument appropriate for the study population?
  • How sensitive is the instrument in detecting small differences in the phenomenon intended to measure?
  • What is the process of obtaining, administering and scoring the instrument?
  • Is there any cost associated with the instrument?
  • What evidence is available related to the reliability and validity of the instrument?

The process of selecting the research instrument is illustrated in [Figure 4].
Figure 4: Process of selecting a research instrument

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  Validity and Reliability Top

Validity of an instrument refers to the degree to which an instrument measures what it is supposed to measure (Polit and Beck, 2012). If an instrument is developed to measure anxiety, it should not have items related to fear, though both are closely related. In other words, the instrument should have items that measures only anxiety. Internal validity and External validity are the two important types of validity to be considered by the researcher. Internal validity is an attribute of a study’s design that contributes to the accuracy of findings. External validity refers to the extent to which the findings can be generalized to other people. According to the kind of information provided and the purpose of the instrument, validity can be classified as content, criterion-related, and construct validity (LoBiondo- Wood & Haber, 2014).

1. Content validity: It represents the universe of content, or the domain of a given variable/construct. Once the researcher develops a tool, the items are submitted to a panel of judges considered to be experts about the concept. Apart from the opinion of the experts about the items, it is also subjected to ratings as expressed by the panel of experts to identify the content validity index (CVI). This is termed as interrater agreement or relevance. A subtype of content validity is face validity, which verifies that the instrument gives the appearance of measuring the concept.

2. Criterion-related validity: Indicates the extent to which the subject’s performance on the instrument and the subject’s actual behavior are related. The degree of correlation of one test with the scores of another more established instrument of the same concept when both are administered at the same time is termed as concurrent validity. The degree of correlation between the measure of the concept and some future measure of the same concept referred to as predictive validity.

3. Construct validity: The extent to which a test measures a theoretical construct, attribute, or trait is known as construct validity.

Reliability of an instrument is the degree of consistency or dependability of the attributes of a variable or a construct. If the instrument brings results similar or close to similar results, it is considered as highly reliable. A reliable instrument should not respond to chance factors or environmental conditions. The stability within an instrument is called internal reliability and the stability of the instrument between two raters is called as inter-rater reliability. The three main attributes of a reliable scale are stability, homogeneity, and equivalence. Stability refers to the ability to produce the same results with repeated testing, homogeneity means that all of the items in an instrument measure the same concept, variable, or characteristic, and equivalence is the ability to produce same result if a parallel or equivalent instrument is used to measure the same attribute (LoBiondo-Wood & Haber, 2014; Polit & Beck, 2012; Wood & Ross-Kerr, 2011).

So, the researcher should test the validity and reliability of an instrument before administering it. Because once the instrument has been administered it cannot be changed and any problems with the instrument after it has been administered will require the researcher to completely re-do the data collection process.

  Conclusion Top

The researcher should undertake the difficult task of developing an instrument only after verifying that one does not already exist. If the researcher wishes to use the existing instrument, permission has to be obtained to use the instrument in writing. Researchers should carefully consider the various factors after a thorough literature review and then select instruments.

Conflicts of Interest: The author has declared no conflicts of interest

  References Top

Brink, P. J., & Wood, M. J. (1989). Advanced design in Nursing Research. Newbury Park, CA: Sage Publications  Back to cited text no. 1
Burns, N., & Grove, S. K. (2011). Understanding Nursing Research: Building evidence based practice (5th ed.). New Delhi: Elsevier Health sciences.  Back to cited text no. 2
Hamilton, M. (1959). The assessment of anxiety states by rating. British Journal of Medical Psychology, 32, 50-55.  Back to cited text no. 3
Lincoln & Guba. (1985). Instrument, validity, reliability. Retrieved from https://researchrundowns. wordpress.com/quantitative-methods/instrument- validity-reliability/  Back to cited text no. 4
LoBiondo-Wood, G., & Haber, J. (2014). Nursing research: Methods and critical appraisal for evidence-based practice (8th ed.). St. Louis, Missouri: Elsevier and Mosby publications.  Back to cited text no. 5
Polit, D. F., & Beck, C. T. (2012). Nursing research: Generating and assessing evidence for nursing practice. (9th ed.). London: Wolters & Kluwer.  Back to cited text no. 6
Richard, M. J. (2013). Educational research: Instruments. Retrieved from www.83.homepage.villanova.edu/ richard.j acobs/ on 27/06/2015  Back to cited text no. 7
Tools of Research. (2015). Retrieved from http://www.mu.ac.in/myweb_test/Research%20Methad ology-Paper-3/Chapter-9.pd.  Back to cited text no. 8
Wood, M. J., & Ross-Kerr, J. C. (2011). Basic steps in planning nursing research: From question to proposal (7th ed.). Sudbury, MA: Jones and Barlett Publishing.  Back to cited text no. 9


  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

  [Table 1]


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1. Questionnaires
2. Scales
Selection of res...
Validity and Rel...
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