Which function is used to determine if a reference is null?

The function used to determine if a reference is null is indeed ISNULL. This function is specifically designed to evaluate whether a given reference contains any value. When ISNULL is applied to a reference, it returns a Boolean value: true if the reference is null (meaning it does not point to any valid data) and false if it contains a value.

Understanding null references is crucial in data handling and programming because null values can lead to errors or unintended behavior if not properly checked. Therefore, using ISNULL allows for proper validation and error handling in scenarios where a reference might not hold any data, thus ensuring the integrity of the data processing flow.

The other functions listed do not serve this purpose. NORMDIST is used for calculating the normal distribution, RAWVALUE is related to fetching the raw value of an object, and MONEYVALUE deals specifically with monetary conversions. Each of these functions serves quite specific uses within data analysis and processes, distinct from validating null references.