The question asks which method is frequently used to ensure that data is correctly entered into a computer. Let's examine the options provided:

1. Input Controls: These are mechanisms that ensure the accuracy and integrity of data as it is entered into a system. They typically include checks and validations, such as data type checks, range checks, and consistency checks, to confirm that the information meets certain criteria before being processed further. This makes input controls the logical choice for ensuring correct data entry.
2. Speakers: Speakers are output devices used to produce sound. They have no role in ensuring data is correctly entered into a computer.
3. Keyboards: Keyboards are input devices used to enter data into a computer. However, they are not responsible for verifying the correctness of the data entered. That responsibility typically falls to input controls.
4. Digitisers: These are devices that convert analog signals into digital data. While they serve an important role in data capture, they do not inherently include mechanisms for ensuring data accuracy during entry.

Based on the above explanations, the correct and most relevant option is Input Controls. They play a crucial role in ensuring that data entered into the system meets predefined accuracy and integrity standards.

Therefore, the correct answer is:

Input Controls