PrepTest 41, Section 2, Question 2
A study of plaque buildup on teeth used three randomly assigned groups of people who brushed their teeth twice a day for a year. People in Group 1 used the same toothbrush all year. People in Group 2 used the same toothbrush all year but sterilized it each month. People in Group 3 used a new, sterile toothbrush each month. At the end of the year, people in Groups 1 and 2 had the same amount of plaque buildup as each other, while people in Group 3 had less plaque buildup.
A study of plaque buildup on teeth used three randomly assigned groups of people who brushed their teeth twice a day for a year. People in Group 1 used the same toothbrush all year. People in Group 2 used the same toothbrush all year but sterilized it each month. People in Group 3 used a new, sterile toothbrush each month. At the end of the year, people in Groups 1 and 2 had the same amount of plaque buildup as each other, while people in Group 3 had less plaque buildup.
A study of plaque buildup on teeth used three randomly assigned groups of people who brushed their teeth twice a day for a year. People in Group 1 used the same toothbrush all year. People in Group 2 used the same toothbrush all year but sterilized it each month. People in Group 3 used a new, sterile toothbrush each month. At the end of the year, people in Groups 1 and 2 had the same amount of plaque buildup as each other, while people in Group 3 had less plaque buildup.
A study of plaque buildup on teeth used three randomly assigned groups of people who brushed their teeth twice a day for a year. People in Group 1 used the same toothbrush all year. People in Group 2 used the same toothbrush all year but sterilized it each month. People in Group 3 used a new, sterile toothbrush each month. At the end of the year, people in Groups 1 and 2 had the same amount of plaque buildup as each other, while people in Group 3 had less plaque buildup.
Which one of the following, if true, most helps to explain the relative amounts of plaque buildup found in the three groups?
The buildup of plaque on teeth, which brushing twice a day helps to prevent, is accelerated by the growth of bacteria on toothbrushes that remained unsterilized for more than a month.
The stiffness of the bristles on new toothbrushes, which the mechanical action of brushing destroys after several months, inhibits the buildup of plaque.
The people who did the study measured the amount of plaque buildup by a new method not usually employed by dentists.
Before they joined the study, some of the people in Group 3 had been in the habit of brushing their teeth only once a day.
The people in Group 2 and Group 3 brushed their teeth as vigorously as did the people in Group 1.
0 Comments