What is data validation and data verification?

Data Validation
Data validation is the process of comparing data with a set of rules to find out if data is reasonable. 

There are many types of data validation such as:
-Format check: Checks data is in the right format, e.g. date in the format dd/mm/yyyy
-Presence check: Checks that data has been entered into a field
-Range check: Checks that a value falls within the specified range, e.g. IB grades can only range between 0 and 7.
-Type check: Ensures the correct data type has been entered, e.g. age should be a number.

Data Verification
Data verification is the process of checking that the data entered exactly matches the original source to find out if data is accurate.

Data verification methods include:
-Double entry - entering data twice
-Proofreading data - someone checks the data entered against the original document
-Echo - system repeats the data being entered