Math for Liberal Studies
What is an identification number? An identification number is a sequence of digits and/or numbers that identifies an object, person, place, or concept The number should unambiguously identify something: no two things should have the same ID number
Where have you encountered ID numbers? License plate Driver’s license number Student ID number Social Security number Phone numbers Credit card numbers ISBN (International Standard Book Number) UPC (Universal Product Code) Many, many more…
Are ID numbers random? What happens if you go to Amazon.com and type in a random sequence of digits for a credit card number?
Security Features How does the computer know that the number you typed in isn’t valid? Should the computer have to look through all the millions of credit card numbers to make sure that yours isn’t on the list?
Checking Validity Most ID numbers have a way to check to make sure that the number is valid This is not just for security, but to detect errors If the ID number is entered incorrectly, it is important that the error is caught
Kinds of Errors Substitution: instead of This error is the most common, occurring almost 80% of the time Transposition: instead of This error accounts for around 10% of all errors Jump transposition: instead of This error is much rarer, accounting for only about 1% of all errors