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Validity and reliability of the instrument
1. Validity and Reliability of the
Instrument
Presented by:
Ms. Bhoomika Patel
Assistant Professor
Sumandeep Nursing college
Sumandeep Vidyapeeth
Sumandeep Nursing College, SVDU
2. Validity
• Validity refers to how well a test measures what it
supposed to measure.
• For example, if an anxiety test measures anxiety and
not other closely related concepts, then it can be
said to be a valid tool for anxiety measurement.
• Types
• Face
• Construct
• Criterion-related
• Content
Sumandeep Nursing College, SVDU
3. Validity
Face validity
• It refers to whether the test appears to be
assessing the intended construct. Experts
ascertain the face validity of a test by looking at
the overall appearance of the test items.
• It is noteworthy that it is not a scientific type of
validity; however, it is an important indicator of
the validity of a test. For example, the researcher
may be able to determine if a person is stressed/
happy just by looking at the face of the individual.
Sumandeep Nursing College, SVDU
4. Validity
Construct validity (pain in amputated patients)
• It is one of the main types of validity along with
content and criterion validity. It is used to ensure
that the test actually measures the intended
construct of interest and not any other.
• Multi-trait multi-method matrix (MTMM) as
described by Campbell and Fiske is an important
method to ascertain construct validity.
Sumandeep Nursing College, SVDU
5. Validity
Criterion-related validity
• It is used to predict the future or concurrent
performance of a test. It is further classified in two
subtypes: concurrent and predictive validity. The test
results are correlated with another concurrent or future
criterion of interest. (professionalism with research
papers,
Content validity
• It ensures that the designed measure covers a broad
range of content within the concept under study. As it is
not possible to cover everything, selected items need to
be sampled from all the domains of the topic.
Sumandeep Nursing College, SVDU
6. Reliability
• The reliability of a data collection instrument
refers to the degree to which it produces
stable and consistent results.
• Types:
• Test –retest reliability
• Internal consistency reliability
• Inter-rater reliability
Sumandeep Nursing College, SVDU
7. Reliability
Test –retest reliability
• It is a type of reliability used to evaluate a test for the
stability of its scores over a period of time.
• If the variable measured by the instrument is liable to
change over a period of time (time effect), then this
method cannot be used to determine the reliability of
the test.
• It is ascertained by administering the same test twice
over a period of time to a group of individuals. The test
scores at Time 1 and Time 2 are correlated to evaluate
the test for stability over time.
Sumandeep Nursing College, SVDU
8. • KARL PERSON’S CORRELATION
r = n(xy)-(x)(y)
{n X2 – ( x)2 } {n y2 – ( y)2 }
If +1: perfect reliability
0: no
More than 0.70: Acceptable
Sumandeep Nursing College, SVDU
10. Reliability
Internal consistency reliability (Homogenesity)
• It is the measure of reliability used to assess the
degree to which different test items that investigate
the same construct of interest produce similar
results. Split-half is one way to assess internal
consistency reliability.
• The test is then administered to a group of subjects
and the total score for each set is computed. Split-
half reliability is obtained by determining the
correlation (r) between the scores of two sets of test
items.
Sumandeep Nursing College, SVDU
11. Reliability
Internal consistency reliability
• Thereafter, the Spearman–Brown prophecy formula
is applied to calculate the split-half reliability
coefficient.
• r = (x-x)(y-y)
• (x-x)2 (y-y)2
Sumandeep Nursing College, SVDU
12. Reliability
Internal consistency reliability
• Cronbach’s alpha is a measure that calculates the
correlation coefficient for all possible half-splits of
test items.
• Therefore, it is considered superior to the split-half
method for estimation of internal consistency of a
test. Coefficient alpha or Cronbach’s alpha is
calculated using the following formula:
Sumandeep Nursing College, SVDU
13. Reliability
Inter-rater reliability (Equivalence)
• It is a measure of the reliability of an observation
checklist.
• Inter-rater reliability of the checklist must be assessed
where two or more observers watch the event
simultaneously and record their observation on the
checklist as per the instructions. It is used to assess the
degree to which different observers agree in their
observation decisions.
Sumandeep Nursing College, SVDU
14. Pilot Study
• A pilot study is a small-scale trial run undertaken
before embarking on the main study to identify
unforeseen obstacles in the execution of the actual
study plan.
• Expensive interventions can be tested to determine
whether they are promising and acceptable to the
participants. It can provide useful data for sample
size determination and the modifications required in
the overall plan of the main study (sampling strategy,
intervention protocols, data collection instruments,
data collection plan, plan of data analysis).
Sumandeep Nursing College, SVDU
15. PURPOSES
• ASSESS FESIBILITY AND PRACTICABILITY
• ASSES AVAILABILITY OF SUBECTS
• ESTABLISH VALIDITY AND RELIABILITY
• HELPS TO FINALIZE DATACOLLECETION PROCEDURES
• UNDERSTAND STUDY VARIABLES AND CONFOUNDING
VARIABLES
• FIND OUT POBLEMS RELATED TO TIME
• REFINING THE METHODOLOGY
• HELPS FOR PLANNING THE DATA ANAYLYSIS
• DETERMINE THE RESOURCES
• CONVENCING THE FUNDING BODIES
Sumandeep Nursing College, SVDU
16. PROBLEMS
• INACCURATE PREDICTIONS AND
ASSUMPTIONS FOR SAMPLE SIZE ESTIMATION.
• RISK OF CONTAMINATION (DON’T INCLUDE
THE DATA OF PILOT STUDY IF RESEARCH PLAN
MODIFIED, NOT CONDUCT STUDY IN SAME
AREA)
Sumandeep Nursing College, SVDU
