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9.6 Standard Deviation

Standard deviation, or variance, is a measure of the closeness of each term to the average (mean). If the terms are all close to the mean or average, then the standard deviation will be small and the mean can be considered an accurate approximation of the distribution.

To calculate to the standard deviation:
1. Compute each deviation as discussed on Section 9.4. 
2. Now, square each deviation and add the results all together. 
3. Finally, divide the calculated total by the number of terms minus one, and take the square root.

Example 1 - Find the standard deviation of this set of fire run distances: 9.0 chains, 12 chains, 11.5 chains, 12 chains, 9.5 chains. 

Step 1. Find the average (see Section 9.3).

9.0 + 12.0 + 11.5 + 12.0 + 9.5 = 54, 54 ÷ 5 = 10.8

Step 2. Find the deviation of each term (see Section 9.4).
9.0 - 10.8 = -1.8
12 - 10.8 = 1.2
11.5 - 10.8 = 0.7
12.0 - 10.8 = 1.2
9.5 - 10.8 = -1.3


Step 3. Square each deviation above.
(-1.8)2 = 3.24
(1.2)2 = 1.44
(0.7)2 = 0.49 
(1.2)2 = 1.44 
(-1.3)2 = 1.69 


Step 4. Add the squared deviations together.
3.24 + 1.44 +0.49 + 1.44 + 1.69 = 8.30 

Step 5. Divide the sum of the squared deviations by the number of terms minus 1.
8.30 / (5-1) = 2.075

Step 6. Find the square root of the difference computed in Step 5.
√2.075 = 1.44

The standard deviation is 1.44 chains.

 

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NWCG Equipment Technology Committee Releases Safety Warning: 24-001 Stihl Chainsaw Toolless Fuel Cap Spill Prevention

Date: November 14, 2024
Contact: Equipment Technology Committee

The Equipment Technology Committee (ETC) has released Safety Warning: 24-001 Stihl Chainsaw Toolless Fuel Cap Spill Prevention. Misaligned toolless fuel caps on Stihl chainsaws have led to recurring fuel spillage, fuel ignition, and burn injuries during wildland fire management operations.

This Safety Warning is intended to highlight the details and recommended procedures for the installation of a Stihl chainsaw toolless fuel cap, as well as how to identify and correct a misaligned, damaged, or broken fuel cap to help prevent fuel spillage.

References:

NWCG Safety Warning: 24-001 Stihl Chainsaw Toolless Fuel Cap Spill Prevention

Advertencia de equipos 24-001: Prevención de derrames de la tapa de combustible sin herramientas de la motosierra Stihl

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The Incident Position Standards and Next Generation Position Task Book are now available for Equipment Time Recorder (EQTR)

Date: November 13, 2024
Contact: Incident Business Committee

NWCG is excited to announce that the NWCG Incident Position Standards for Equipment Time Recorder, PMS 350-51 and NWCG Position Task Book for Equipment Time Recorder (EQTR), PMS 311-51 are now available.

The Performance Support Package, which for EQTR, includes the Incident Position Standards and Next Generation Position Task Book were developed through the Incident Performance and Training Modernization (IPTM) effort. The Performance Support Package will support trainees, those qualified in the position, and evaluators.

References:

NWCG Equipment Time Recorder Position Page

NWCG Incident Position Standards for Equipment Time Recorder, PMS 350-51

NWCG Position Task Book for Equipment Time Recorder (EQTR), PMS 311-51

The Incident Position Standards and Next Generation Position Task Book are now available for Personnel Time Recorder (PTRC)

Date: November 13, 2024
Contact: Incident Business Committee

NWCG is excited to announce that the NWCG Incident Position Standards for Personnel Time Recorder, PMS 350-53 and NWCG Position Task Book for Personnel Time Recorder (PTRC), PMS 311-53 are now available.

The Performance Support Package, which for PTRC, includes the Incident Position Standards and Next Generation Position Task Book were developed through the Incident Performance and Training Modernization (IPTM) effort. The Performance Support Package will support trainees, those qualified in the position, and evaluators.

References:

NWCG Personnel Time Recorder Position Page

NWCG Incident Position Standards for Personnel Time Recorder, PMS 350-53

NWCG Position Task Book for Personnel Time Recorder (PTRC), PMS 311-53

NWCG Risk Management Committee Releases Safety Bulletin: 24-001 Use of Respirators on Wildland Fires

Date: November 7, 2024
Contact: Risk Management Committee

The Risk Management Committee (RMC) has released Safety Bulletin: 24-001 Use of Respirators on Wildland Fires. As wildland fire respirators are available through several established vendors, wildland fire personnel need to understand regulations and limitations of respirator use in the workplace.

Safety Bulletin 24-001 outlines the following topics regarding respirator use for wildland fires:

  • Requirements for Respirator Use
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This bulletin also provides mitigation recommendations to help reduce smoke exposure for wildland firefighting efforts.

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NWCG Safety Bulletin: 24-001 Use of Respirators on Wildland Fires

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