Answer:
A) The greater the variance within the population, the larger the sample should be.
Explanation:
The variance of a sample mean is inversely proportional to the sample size, that is, the larger the sample size the smaller the variability of the sample. When sample size increases, the range decreases and hence the variance decreases resulting in a more accurate research result with minimal experimental error.
Hence the researcher should employ a large sample size to reduce the variation in the population.
Answer:
A retrospective cohort study
Explanation:
A cohort study is an observational study in which individuals are classified (or selected) according to exposure status (exposed and unexposed) and followed to assess the incidence of the disease over a given period of time. Cohort studies can also be used to assess the risks and benefits of using a particular medication.
In the case of the research exposed in the question, one researcher analyzed the city's records to see who among the city's retirees had spent their careers working mostly indoors, without sun exposure; and outdoors with sun exposure. The sun is a major cause of hair cancer. Once participants were enrolled and screened, the scientist researched and examined the incidence of any form of skin cancer. This is a perfect example of a retrospective cohort study.
Explanation:
While Eli Whitney is best remembered as the inventor of the cotton gin, he was also the father of the mass production method. In 1798, he figured out how to manufacture muskets by machine so that the parts were interchangeable. It was as a manufacturer of muskets that Whitney finally became rich. He died in 1825.
