The Predictor of Height: Arm Span

In school, we always need to measure and record our height and weight when there is a physical fitness test. When you are the one in charge of the measuring station, do you ever get irritated by how long it takes, to help so many people measure their height?

It is also cumbersome to keep adjusting the movable plane of the equipment, in order to get accurate readings. It causes much inconvenience, especially if many of the people in line are of very different heights.

And...

What about when the many people in line are much taller than you!?

> If we can use the measurements of other body sites,

for example, the distance between one's outspread arms to predict our height...

Mass health screening exercises carried out at polyclinics or community centres would be done much more quickly and efficiently!

Hence for our Statistic project, we decide to examine the relationship between arm span and height.

Our Research Hypothesis (H1)

: There is a relationship between arm span and height


As for the Null Hypothesis (Ho),

: There is no relationship between arm span and height

Variables involved:

Independent Variable (IDV) - Arm Span

Dependent Variable (DV) - Height

Extraneous Variable (EV) - Age, Sex, Genes, Diet, Ethnic group


Questions...

1. Does arm span predict height of a person?

2. Can arm span measurement be used
> interchangeably with height?
3. Does arm span correlate with height?

Literature Review

More than 400 years ago, Leonardo Da Vinci proposed that the length of a man's outspread arms is equal to his height (Drexel Universiy, 2009).

Leonardo Da Vinci was a scientist, engineer and mathematician. He was more famous for his works as a artist though.

Leonardo's proposal is also supported by recent studies.(Brown et al., 2000) stated that arm span is a valid measure of height.

However, they only carried investigations of this research on young and middle-age adults. Accuracy is improved using a prediction equation derived from regression analysis. This article requires further studies to support the claim that arm span is proportional to a person's height.

In a follow-up study done by Ohio State University, (Brown et al., 2002), research is done on using a age range of 19 to 67. The study also compared self-reported height and arm span measurement to actual height, to determine their level of accuracy.

Self-reported height data is found to be closer to actual height measurements.

Though so, arm span measurements were still shown to be accurate enough as an alternative for measured height, when neither measured height nor self-reported height are available. This research used test-retest reliability as a control, ensuring a very strong reliability (r=0.997) for both arm span and height measurements.

The research findings suggest that we can trust patients to give a reliable answer about their height during health assessment

During research, we also found out that arm span measurements are used as a substitute for standing height in clinical settings (Parker et al., 1996). The research was done by staff in the Department of Pulmonary and Critical Care Medicine, Walter Reed Army Medical Center, Washington, D.C., USA. The measurements were used in predicting lung volume in patients unable to stand or with *thoracic abnormalities.

This research article studied the relationship between standing height, arm span, race, sex, and age in 202 patients, aging from 20 to 88, that were referred for screening spirometry. Multiple linear regression analysis found arm span, race, sex, and age to be predictive of standing height (r2 = 0.8659, p <0.0001>).

In all the studies reviewed, arm span measurement is found to be reliable enough to be used to predict measured height.

*thoracic refers to the chest

Purpose
The purpose of this study is to evaluate whether there is a strong relationship between arm span and height measurement, whether arm span is a good predictor of actual height.

Conceptualization

Arm Span is defined as

the distance from one end

of the tip of the middle

finger to the other end

with the back straight,

arm stretched sideways,

parallel to the ground and

palm facing outwards.

Height is defined as

the distance between

the lowest and highest

pointsof a person

standing upright with

bare feetand heels

together. (SpirXpert, 2009)

Operationalisation

A standard 5m x 16mm measuring tape
was used to measure arm span and height.

Means of arm span and height measurements were calculated using a Casio fx- 350MS calculator.

Method

Target Audience
: Students of NYP

Sample

A convenience sample of 40 students were recruited from Nanyang Polytechnic's library cafe and along the corridors of School of Health Science (SHS), Level 2.

Data-Collection Procedure

The Main Fieldwork Investigators, Bishu Pun and Lin Qiu, were in charge of handling the

equipments and getting the measurements for height and arm span. They were trained by the

Main Data Analysis Investigator is to train the Main Fieldwork Investigators to adhere to the standardized measurement procedures.

The research team approached students in the library cafe and along SHS Level 2 corridor to ask for their participatioin in the study.

The students were informed of the study's purpose, duration of data collection required and that confidentiality is assured. No identifying

particpant data were collected, and each participant was assigned a number.

Data was collected on 8 June 2009, from 2pm to 5.30pm. Height and arm span was taken as operationalised, to maintain internal validity.For height measurement,

1. The subject should have bare feet, and the heels together.
2. Heels, calf, buttock and back should preferably touch the stadiometer.
3. Record standing height in mm, refrain from rounding at this stage.

These were the data collection forms:

Two height measurements and two arm span measurement were obtained for each participant.

This is to ensure intra-rater reliability.

The total time required by the participant to complete the study was approximately 4 minutes.

For each participant, the mean height and arm span were used for calculations.

Data Analysis

Scatterplot

Computing Pearson's Correlation Coefficient

Computing Regression EquationRESULT

The scatter appears to follow a general positive linear trend. There is no violation of the linearity assumption. The chosen level of significance is a= 0.05.

There is a positive, very strong, and significant relationship between arm span and height. (r = 0.923, p<0.05, n =" 40)" style="font-size:100%;">Null hypothesis is rejected.

The linear equation is : Y = m (x) + c

> Height = 0.731 (Arm Span) + 43.839

Discussion

The researchers' findings back up the literature review. Prior research has already indicated that the use of arm span length to predict height is accurate enough to be used as a predictor of height ( Brown, et al., 2000; Brown, et al., 2002;Parker, et al., 1996). Our findings strengthen external reliability.

In clinical settings, we nurses can apply this research findings when measuring height, be it for calculating base mass index or general documentation in nurses' casesheets.

Limitations of Study/Needs for Improvement
The research procedures should have been prepared much more earlier. The study could have been more representative if the researchers collected data from more locations around the school.

Reflection

After a semester of HS2135, Statistics, our sub-group has learnt about simple terms commonly used in research. For example the term, null hypothesis, mutually exclusive, the difference between nominal, ordinal and scale data, and also reliability and validity.

We are also sufficiently competent in using SPSS for simple data analysis. The importance of literature review is also realised. For research projects, teamwork is essential for planning the study, carrying it out and finally analysing the data. If not, the workload would not be equally divided, ensuring efficency.
Through data collection, we also learnt how to approach strangers and explain to them about our study.

What is interesting is that we learnt to integrate what we learnt in HS2134, Research Method with statistics. For example, the concept of sampling, validity and reliability.

All the skills or knowledge gained will help us after we graduate and when we need to carry out research to improve our nursing care for patients.

Conclusion

The null hypothesis Ho is rejected. There is a relationship between arm span and height. Leonardo Da Vinci's proposal that arm span and height being equal was not supported. The research findings showed that arm span and height findings are close, but they are not equal. Despite the fact that Leonardo was wrong in his proposal, it is still admirable that someone actually observed the similarity in arm span and height measurements long before the modern era.

We will be delighted if blog visitors read through the whole report and learn something as a result.

References are posted on another blog entry.