Detailed Instructions: This task is about translating a given Spanish language sentence to English.
Q: En este libro, en esta investigación estudiamos cerca de 30,000 personas.
A:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
In this book, in this research we've basically tested about 30.000 people.