Weird ASME rounding rule regarding fractional decimals.

In summary, there is a rule in engineering graphics that states when rounding a number with a 5 in the last digit, the digit before it is odd, and there are no other digits beyond the 5, the last digit will be increased by 1. If the digit before the 5 is even, the last digit will remain unchanged. This rule is meant to prevent information loss and is based on the concept of rounding to even. This method ensures that the average of rounded numbers stays the same.
  • #1
Jae
10
0
I'm taking an engineering graphics class and I recently learned this rule which states:

"When the digit next beyond the last place to be retained is 5, and there are no digits beyond this 5, or only zeros, increase by 1 the digit in the last place retained if it is odd, leave the digit unchanged if it is even. Increase by 1 the digit in the last place retained, if there are digits beyond this 5."

It just sounds too stupid to be true. What's the purpose of such a rule?
 
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  • #2
The 5 will be lost.
When you do not have the information needed to decide whether to round up or down, then you round to even.
15.5 will round to 16.
16.5 will round to 16.
17.5 will round to 18.
18.5 will round to 18.

The rounding method does not change the average.
 

FAQ: Weird ASME rounding rule regarding fractional decimals.

What is the ASME rounding rule and why is it considered weird?

The ASME rounding rule is a mathematical formula used to round fractional decimals to the nearest even number. It is considered weird because it differs from the commonly used rounding rule (rounding up if the decimal is 5 or greater) and can lead to unexpected results.

How does the ASME rounding rule work?

The ASME rounding rule works by first truncating the decimal to the specified number of digits, and then rounding up if the last digit is 6 or greater, and rounding down if the last digit is 4 or smaller. If the last digit is a 5, the number will be rounded up if the digit preceding it is odd, and rounded down if it is even.

Why was the ASME rounding rule created?

The ASME rounding rule was created to avoid bias in rounding numbers. In traditional rounding methods, numbers ending in 5 are always rounded up, which can lead to a slight bias towards higher numbers. The ASME rounding rule aims to eliminate this bias by rounding to the nearest even number.

Can the ASME rounding rule be used in all situations?

No, the ASME rounding rule is typically only used in specific industries, such as engineering and finance, where precision is crucial and bias in rounding can have significant impacts. In most other situations, traditional rounding methods are sufficient.

Are there any other rounding rules besides ASME and traditional rounding?

Yes, there are other rounding rules such as the round-half-up rule (rounding up if the decimal is 5 or greater), the round-half-down rule (rounding down if the decimal is 5 or greater), and the round-half-odd rule (rounding up if the decimal is 5 and the preceding digit is odd). These rules are used in different industries and situations, depending on the desired level of precision and potential biases.

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