Question

Explain why the following may lead to useless data

1.1To determine the proportion of improperly filled cans of paint, an inspectors at the filling machine examines every 10th can as it leaves the filling machine

1.2To determine how voters in a city feel about an issue, a pollster randomly selects a page in the telephone directory and calls every telephone number on the page.

1.3The wheat in several freight cars is sampled by taking samples from the top of each car.

Answer 1

1.1 . To determine the proportion of improperly filled cans of paints , inspector should choose random cans of paint insted of choosing every 10th can , say a sample of 30 or more than 30 cans at random.

1.2. To determine how voters in a city feel about an issue a pollster should randomly select some number of people in each page and call them insted of selecting a page in the telephone directory as it will not reveal proper amount of information about the voters.

1.3. The wheat of several direct cars should be sampled by selecting samples from the top middle and the lower part of each freight insted of selecting sample only from the top .