Likelihood Rating Scale - Calculation on Probability

[Andre833]

I came across the following table on page 6 from publication at : https://www.researchgate.net/publication/320008411

Ranking​	Probability​	Description​
1​	0.00001​	Improbable unlikely to occur at all
2​	0.0001​	Remote - once in 100 to 1000 years on one ship
3​	0.001​	Rare once in 10 to 100 years on one ship
4​	0.01​	Occasional - once in 1 to 10 years on one ship
5​	0.1​	Frequent once in one year on one ship

I am confused at how the probability number is calculated in the above table.

Example, if definition of rank 4 is it happens once in 10 years, the probability is 1/10 = 0.1. How did the table state 0.01?
Is my interpretation of once in 10 years = 1/10 is the calculation of frequency?
So how is the table column probability number being calculated.

 

[Deleted member 4993]

I came across the following table on page 6 from publication at : https://www.researchgate.net/publication/320008411

Ranking​	Probability​	Description​
1​	0.00001​	Improbable unlikely to occur at all
2​	0.0001​	Remote - once in 100 to 1000 years on one ship
3​	0.001​	Rare once in 10 to 100 years on one ship
4​	0.01​	Occasional - once in 1 to 10 years on one ship
5​	0.1​	Frequent once in one year on one ship

I am confused at how the probability number is calculated in the above table.

Example, if definition of rank 4 is it happens once in 10 years, the probability is 1/10 = 0.1. How did the table state 0.01?
Is my interpretation of once in 10 years = 1/10 is the calculation of frequency?
So how is the table column probability number being calculated.

Please show us what you have tried and exactly where you are stuck.​

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[Andre833]

From the table below, i am trying to understand how is the probability column calculated based on its description column.

Ranking	Probability	Description
1	0.00001	Improbable unlikely to occur at all
2	0.0001	Remote - once in 100 to 1000 years on one ship
3	0.001	Rare once in 10 to 100 years on one ship
4	0.01	Occasional - once in 1 to 10 years on one ship
5	0.1	Frequent once in one year on one ship

I have tried looking at the description column but came up with answers that does not match the numbers in the probability column.
Following are my example work calculations on what i tried base on my thought of probability.

Ranking 2 description is "once in 1000 years" which is equal to 1/1000=0.001 but why is the probability column showing 0.0001
Ranking 3 description is "once in 100 years" which is equal to 1/100=0.01 but why is the probability column showing 0.001
Ranking 4 description is "once in 10 years" which is equal to 1/10=0.1 but why is the probability column showing 0.01
Ranking 5 description is "once in 1 year" which is equal to 1/1= 1 but why is the probability column showing 0.1
Am i missing something in my probability calculation?

 

[Dr.Peterson]

The whole thing, of course, is fuzzy! I don't think they're trying to make anything too specific.

My best guess is that, since they didn't say what event they are giving probabilities for, it may be "something goes wrong in a given month" (or tenth of a year or so). Then 1/10 each month would add up to around 1 per year.

I tried skimming the article and didn't see anything about a time scale.

 

[Andre833]

Thanks for your reply Dr.Peterson.
Noted that i have to say about the event. Thus to make the table correct, is my below explanation and interpretation of the table and its calculation be correctly written?

Ranking 2 description is "once in 100 yrs to once in 1000 years". Thus if this event was to happen 1/10 of the time between year 100 and year 1000, the probability is equal to 1/1000/10 =0.0001.

Ranking 3 description is "once in 10 yrs to once in 100 years". Thus if this event was to happen 1/10 of the time between year 10 and year 100, the probability is equal to 1/100/10 =0.001.

Ranking 4 description is "once in 1 yrs to once in 10 years". Thus if this event was to happen 1/10 of the time between year 1 year and year 10, the probability is equal to 1/10/10 =0.01.

Ranking 5 description is "once in a 1 year". Thus if this event was to happen 1/10 during a year, the probability is equal to 1/1/10 =0.1.