A sample is to be taken from a list of names that are on cards (one name to a card) numbered consecutively in a file. Each name is to have an equal chance of being drawn in the sample. What problems arise in the following common situations?

Some of the names do not belong to the target population, although this fact cannot be verified for any name until it has been drawn.

Some names appear on more than one card. All cards with the same name bear consecutive numbers and therefore appear together in the file.

Some names appear on more than one card, but cards bearing the same name may be scattered anywhere about the file.

Why would a convenience sample of college students on vacation in Fort Lauderdale, Florida, not be representative of the students at a particular college or university?

Why is the method of selecting the sample even more important than the size of the sample?

A large school district wishes to obtain a measure of the mathematical competency of the junior high students in the district. The district consists of 40 different junior high schools. Describe how you could use cluster sampling to obtain a measure of the mathematical competency of the junior high school students in the district.

A large school district wishes to obtain a measure of the mathematical competency of the junior high students in the district. The district consists of 40 different junior high schools.

Explain how you could use stratified sampling to determine the mathematical competency of the junior high students in the district.