What does it mean for a lake to be stratified? What kind of tests can be done to show whether a lake is or is not stratified? Please explain in detail.
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In a study of cardiovascular disease researchers are concerned about the potential of smoking to be a confounding factor of cholesterol for the outcome of cardiovascular disease. Which of the following are ways to control for the confounding effects of smoking when studying the effect of cholesterol on cardiovascular disease? Choose all that apply and none that do not.
Use a stratified sampling technique to ensure even numbers of smokers and non-smokers | ||
Used a stratified analysis and analyze the effect of cholesterol on cardiovascular disease separately in smokers and non-smokers | ||
Restrict the study to only smokers or non-smokers. | ||
Use a larger sample size to ensure a large number of non-smokers | ||
Use a multivariate model that controls or adjusts for smoking status. | ||
Use a prospective design that allows for temporal relationships between cholesterol and cardiovascular disease |