A statistics that describes the interval of scores bounded by the 25th and 75th percentile rank is?

RUHS, Jaipur, M.Sc Nursing Entrance Exam-2016

Nursing Research & Statistics

Easy

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2016

Explanation

The Inter-quartile range (IQR) is specifically defined as the difference between the 75th percentile (Third Quartile, Q3) and the 25th percentile (First Quartile, Q1).
This range encompasses the middle 50% of the data points in a distribution.
The question directly asks for the term describing the interval between the 25th and 75th percentiles, which is the definition of the IQR.
Unlike other measures like standard deviation, the IQR is a robust measure of spread because it is not influenced by extreme values or outliers.

Option A: A confidence interval is an inferential statistic used to estimate a range in which a population parameter (like the population mean) is likely to fall. It does not describe the spread of scores within a sample.
Option C: Standard deviation measures the average dispersion or variability of data points from the mean of the dataset. It is sensitive to outliers and does not specifically use percentiles in its primary definition.
Option D: Variance is the square of the standard deviation. It also measures the spread of data around the mean but is expressed in squared units, making it less intuitive to interpret than the standard deviation.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Measures of statistical dispersion as background academic context rather than a clinical decision trigger.
Nurses frequently encounter statistics when reading research articles to apply evidence-based practice. Understanding terms like IQR helps in critically appraising the results, such as the variability in patient recovery times or the spread of lab values in a study population.
When a study reports the median and IQR, it often suggests the data is skewed. This is a crucial clue for a nurse to understand that a few patients might have had very different outcomes (e.g., much longer or shorter hospital stays) than the majority.
What if? If a dataset of patient weights had a few extremely high values (outliers), the standard deviation would be large and potentially misleading. The IQR, however, would provide a more stable and representative measure of the spread of weights for the central 50% of patients.

How to Approach the Question

This is a factual recall question that tests your knowledge of basic statistical definitions.
First, break down the question stem: it asks for a statistic describing the 'interval...bounded by the 25th and 75th percentile'.
Recall the definitions of quartiles: Q1 is the 25th percentile, and Q3 is the 75th percentile.
Evaluate the options based on this. The term 'Inter-quartile range' directly relates to the interval between quartiles.
Eliminate the other options: 'Standard deviation' and 'Variance' relate to the mean, not percentiles. 'Confidence interval' is for estimating population parameters, not describing sample spread in this way.

Concept Tested & Keywords

QIQRxF0HQtVW7hg2ds5_7e

E6 NursingResearch Suresh Sharma 5e Part 2 pp. 135-137, 136-138

E6 NursingResearch Sukhpal Kaur p. 456-458