Data Accuracy

4 errors that programs should look for in data

(1) test data type and format, (2) test data reasonableness, (3) test data consistency (4) test for transcription and transposition errors

hard to check for

Transcription and Transposition Errors

Transposition Error Example

Typing 7754 instead of 7745

transcription error

typing the wrong character

GIGO

Garbage In, Garbage Out

test data type and format example

2/a/96 is not a date, If a phone number should have exactly 10 digits with the area code, then 555-123 is not acceptable.

test data reasonableness examples

231 should not be a person's age, A sale of $50,000 worth of chewing gum at the corner market is probably missing a decimal point somewhere!

A famous slogan in computing sums up the importance of accurate data

GIGO

Examples for testing for transcription errors

Typing 7754 instead of 7154

test data consistency examples

A man's death date should be later than his birth date, The sum of the monthly paychecks should be the same as the total paid for the year.

Conclusions

No better than the data they are based on.

A major task for any program that accepts data

Trying to guarantee the accuracy of the input. Some kinds of errors cannot be caught but many of the most common kinds of mistakes can be spotted by a well-designed program.

transposition error

interchanging two correct characters.