At an assembly 7 out of 10 students who entered the gym were carrying a backpack. Based on this information, if 700 students were at the assembly, how many students could be expected to be carrying a backpack?

A public library asked every 10th person who entered to name the type of book they were getting

The Student Council asked every tenth student in the lunch line how they preferred to be contacted with school news. The results are shown in the table. Is this an unbiased sample? If yes, suppose there are 684 students at the school. How many can be expected to prefer E-mail?

A hospital wants to open a gym. They ask the night-shift ER staff when they would use the gym.

A radio station asks its listeners to dial one of two numbers to indicate their preference for one of two candidates in an upcoming election. Of the responses received, 76% favored candidate A. If there are 1,500 registered voters, how many will vote for candidate A?

To determine the number of umbrellas the average household in the United States owns, a survey of 100 randomly selected households in Arizona is conducted. Of the households, 24 said that they own 3 or more umbrellas. The researcher concluded that 24% of the households in the United States own 3 or more umbrellas. Is the this a valid conclusion? Justify your answer.

A company makes DVDs and randomly selects 25 from 1500 to test them to see if they work.