The variables that affect earning a PhD can vary depending on the field of study and the institution. However, some common factors that can influence the duration and cost of earning a PhD include:

• Research topic: The research topic you choose can impact the time and resources required to complete your PhD. Some topics may require more extensive research, while others may require more specialized equipment or resources.
• Institution: The institution you choose to attend can also affect the time and cost of earning a PhD. Some institutions may offer more funding opportunities or have more resources available to support research.
• Advisor: Your advisor can play a significant role in the success of your PhD. A supportive and knowledgeable advisor can help guide your research and provide valuable feedback.
• Funding: Funding can be a critical factor in the duration and cost of earning a PhD. Some students may receive funding through grants, scholarships, or research assistantships, while others may need to pay for their education out of pocket.
• Time commitment: Earning a PhD can be a time-consuming process that requires a significant commitment of time and energy. The amount of time required to complete a PhD can vary depending on the field of study and the research topic.

These are just a few of the many variables that can impact the process of earning a PhD. If you have any further questions, please let me know.