How to determine sample size for known population

Global Population8,000,000,000±1%Even with modern census methods, counting world population has challenges like migration and remote areas.~9,600YouTube Monthly Users2,700,000,000±3%Distinguishing between active users (daily/weekly) vs occasional viewers affects count accuracy.~1,100Population of India1,400,000,000±1%Despite regular census, rapid population changes and rural areas make exact counting difficult.~9,600Netflix Subscribers230,000,000±5%Monthly subscriber count fluctuates due to free trials, account sharing, and cancellations.~400Population of Luxembourg645,000±2%Small geographic area and strong administrative systems enable more accurate counting.~2,400Students in Online Course50,000±10%Difference between enrolled students and those who actually participate affects accuracy.~100Blue Whale Population10,000±40%Ocean size, whale migration patterns, and limited tracking technology create high uncertainty.~6Everest Climbers6,000±10%Variations in counting methods (successful summits v

how is sample size determined

how do we calculate sample size