The Baldwin family walked four over five of a mile in four over nine of an hour. What is their unit rate in miles per hour?

four-ninths over four-fifths equals four over nine mile per hour
four-fifths over four-ninths equals one and four-fifths miles per hour
four-ninths over four-fifths equals one and four-fifths miles per hour
four-fifths over four-ninths equals four over nine mile per hour

Researchers are conducting experiments to determine the role of alcohol in the development of depression. after the study is complete, they determine that the relative risk of developing depression is 1.55 with a 95 % ci of 1.2 -1.9. each group is then divided into nonsmokers and smokers. the relative risk for the nonsmokers is 1.12 with a 95% ci of 0.87-1.37. the relative risk for the smokers is 1.7 with a 95 % cl of 1.5-1.9. what type of bias may affect this study? a. procedure bias b. recall bias c. selection bias d. confounding e. lead-time bias