# Can “probability” be used interchangeably with “rate”?

In a document about a barcode reader, I came across an expression "scanning probability" to indicate the percentage of successful reading of barcodes by the barcode reader in question.

I would use "scanning rate", but can "scanning probability" also mean the same thing? To me "probability" seems more like "possibility" and does not apply to the case.

• Probability and rate are probably closely related in that the faster you try to scan the lower your probability of a correct scan becomes. – Jim Nov 7 '14 at 8:08

## 2 Answers

Rate on it's own implies speed, so scanning rate would be how fast the scans are done - scanning success rate would be closer, but I personally don't like the expression "scanning probability" much either. Is it the chance that something got scanned, the chances of a detected error, the chances of an undetected error, etc.

# Expanded Answer

Sorry in advance for a technical digression on a language usage site but, to my mind, incorrect and imprecise usage of technical language is inexcusable and in some contexts it can actually be criminal.

As I see it there are a number of possibilities that really should be covered when talking about a bar code reader:

• Good Bar Code is correctly accepted - this is one form of success - True Positive
• Bad Bar Code is correctly rejected - also success - True Negative
• Good Bar Code is rejected - failure - False Negative
• Bad Bar Code is incorrectly accepted - failure - False Positive
• Good Bar Code is accepted but with the wrong value returned - Incorrect Value
• None Bar Code is accepted as a valid bar code - Spurious Returns

These would normally be denoted in terms of the 100% achieved on a single scan.

All of the above will be measures of the reliability of the results of scanning and for a really meaningful picture of how useful the scanner is all 4 need to be enumerated, e.g. if a scanner is to be used to track drugs administered to patients you would rather have to scan more than once to get the correct results than have any erroneous input.

There can also be, for some coding schemes such as QR Code, a percentage of damage to the bar code that can be sustained and still give the True & Accurate results above. This is normally stated as a measure of the robustness and redundancy of the encoding scheme.

• Thank you for your reply. Yes, it is to express the chance something got scanned. Could you suggest other expression? – Jun Kyoto Nov 7 '14 at 8:21

I share your dislike of the term "scanning probability". Although the ratio of successful scans to total scans can be related to a probability for success, you are probably not interested in the outcome of a single scan but in the average success rate over many scans.

As pointed out by @Steve Barnes,

Scanning rate

refers to the speed with which scans can be carried out (e.g, how many scans per minute).

An online search suggests that the terms

Scanning success rate

and

Scanning hit rate

are quite common in this context. Scanning success rate was also suggested by @Steve Barnes.