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Many people treat a condition called “dry eye” with a eye drops.  An eye doctor plans to conduct a study to investigate the following claim made in a recent report. For people with a condition called “dry eye”, there is a difference between the proportion cured by using Eye Drops A and the proportion cured by using Eye Drops B. The doctor will randomly assign 200 volunteers with the eye condition to use one of two eye drops, with 100 assigned to use Eye Drops A  each day and the remaining 100 assigned to use Eye Drops B each day. The doctor will record the number of people cured after six months for each eye drop. (a) Describe the benefit of randomly assigning the type of eye drops to the volunteers. (b) Describe a process that can be used to randomly assign the 200 volunteers to the two eye drops.

New electric lights and powerful machinery allowed factories to run twenty-four hours a day, seven days a week.

The realities of urban dwellers’ lives varied dramatically based on where they fell in the social chain.

Which of the following orbitals are not possible?

The familiar phenomenon of a rainbow results from the diffraction of sunlight through raindrops. Which of the following colors would have the highest frequency?

Which element is represented by the orbital diagram below?

Which of the following brought the majority of Chinese immigrants to the United States during the western expansion?

Americans were overwhelmed by the rapid pace and scale of change at the close of the nineteenth century.

Which of the following describes the U.S. Army’s actions after the Sioux victory at Little Bighorn?

While some pioneer women found extra employment in nearby settled towns, most worked on the farms on which they lived.