Final answer:
The ratio of male to female conceptions in a population is called the primary sex ratio. It is subject to various factors and is different from the secondary sex ratio, which is measured at birth.
Step-by-step explanation:
The ratio of male to female conceptions in a population is called the primary sex ratio. This ratio is influenced by a variety of factors including biological, environmental, and cultural influences. The primary sex ratio is the one present at conception, whereas a slightly different measure, known as the secondary sex ratio, refers to the ratio at birth. The natural sex ratio is approximately 105 male births for every 100 female births. However, this ratio may differ in different parts of the world due to various reasons, including cultural practices, government policies, and economic factors. In the context of your study's findings of 60 girls and 90 boys born out of 150 births which equals to a ratio of 100:150 or 46.67% girls, it would closely match the reported figure in China of 46.7% girls, albeit it is recommended to have a larger sample size for a more accurate assessment.