# Bosenberg's (1995) Paper and SED Data

## Notes

Bosenberg, A. T. (1995) "Skin-epidural distance in children." Anaesthesia. 50: 895-897.
• SED Data (digitized from paper figure): Bosenberg1995.csv
• Scanned image from the Bosenberg (1995) paper: Bosenberg1995.png
• Digitized SED figure from the Bosenberg paper (Fig. 2): Bosenberg1995.svg
• Fitted linear regression line: `SED = 3.93 + 0.80 * WT`, where `SED` is in mm units, and `WT` is in kg units (R2 = 0.74).
• From the paper:

Statistical methods: Regression analysis using the least squares procedure was used to determine the association between the skin-epidural distance and weight. For the difference between the two equations, i.e. the regression equation and the hypothesised 1 mm = 1 kg body weight, a Z-test was performed.

In children over 10 years (n = 19) there was also poor correlation. The data from these patients were not used for further analysis.

Plotting the best fit regression line and its 95% confidence limits shows that the y = x line, or skin-epidural distance (mm) is equal to weight (kg) falls within these limits for weight <40 kg (or 10 years of age) in this series (Fig. 2). Therefore the difference between any two points on these two lines is not statistically significant.

In addition a Z-test performed on any two points obtained from the two equations for a specific weight, i.e. skin-epidural distance (mm) = 0.80 weight (kg) 3.93, and skin-epidural distance (mm) = weight (kg) was found to be not statistically significant.

...

In summary, we have demonstrated that 1 mm/kg is a useful guideline for judging the skin-epidural distance in children between 6 months and 10 years of age.

## Discussion Points

• Was the confidence band really a prediction band?
• Was it simultaneous or pointwise?
• Was Bosenberg's reasoning sound?
• How can we verify Bosenberg's conclusions?

## Assignment

Modify the Bosenberg Sweave file from the previous assignment as follows, and regenerate the PDF report. Ensure that the document remains reproducible.
1. Add Bosenberg's simplified prediction rule (i.e., 1 mm/kg) to the scatterplot.
2. Modify the figure caption to reflect the addition above.
3. Use a statistical technique to assess whether Bosenberg's simplified rule was reasonable.

## Solution

Here is one solution to the assignment above: Bosenberg.Rnw Bosenberg.pdf
Topic attachments
I Attachment Action Size Date Who Comment Rnw Bosenberg.Rnw manage 4.2 K 01 Oct 2012 - 08:51 MattShotwell Solution to the Bosenberg assignment pdf Bosenberg.pdf manage 89.3 K 01 Oct 2012 - 08:52 MattShotwell Solution to the Bosenberg assignment png Bosenberg1995.png manage 38.6 K 17 Sep 2012 - 07:56 MattShotwell Scanned image from the Bosenberg (1995) paper. svg Bosenberg1995.svg manage 185.3 K 16 Sep 2012 - 10:02 MattShotwell Digitized SED data from Bosenberg (1995) paper
Topic revision: r4 - 01 Oct 2012, MattShotwell

• Biostatistics Webs Copyright © 2013-2022 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding Vanderbilt Biostatistics Wiki? Send feedback