# 8. Populations, Samples, and Probability Flashcards

Population

Any complete set of observations (or potential observations).

Sample

Any subset of observations from a population.

For each ot the following pairs, indicate with a Yes or No whether the relationship between the first and second expressions could describe that between a sample and its population, respectively.

students in the last row; students in class

Yes, it is a real population.

For each ot the following pairs, indicate with a Yes or No whether the relationship between the first and second expressions could describe that between a sample and its population, respectively.

citizens of Wyoming; citizens of New York

No. Citizens of Wyoming aren’t a subset of citizens of New York.

20 lab rats in an experiment; all lab rats, similar to those used, that could undergo the same experiment

Yes, it is a hypothetical population.

For each ot the following pairs, indicate with a Yes or No whether the relationship between the first and second expressions could describe that between a sample and its population, respectively.

all U.S. presidents; all registered Republicans

No. All U.S. presidents aren’t a subset of all registered Republicans.

two tosses of a coin; all possible tosses of a coin

Yes, it is a hypothetical population.

Random Sampling

A selection process that guarantees all potential observations in the population have an equal chance of being selected.

Indicate whether the following statement is True or False. A random selection of 10 playing cards from a deck of 52 cards implies that

the random sample of 10 cards accurately represents the important features of the whole deck.

False. Sometimes, just by chance, a random sample of 10 cards fails to represent the important features of the whole deck.

Indicate whether the following statement is True or False. A random selection of 10 playing cards from a deck of 52 cards implies that

each card in the deck has an equal chance of being selected.

True.

Indicate whether the following statement is True or False. A random selection of 10 playing cards from a deck of 52 cards implies that

it is impossible to get 10 cards from the same suit (for example, 10 hearts)

False. Although unlikely, 10 hearts could appear in a random sample of 10 cards.

any outcome, however unlikely, is possible.

True.

Describe how you would use the table of random numbers to take a random sample of five statistics students in a classroom where each of nine rows consists of nine seats.

There are many ways. For instance, consult the tables of random numbers, using the first digit of each 5-digit random number to identify the row (previously labeled

1, 2, 3, and so on), and the second digit of the same random number to locate a particular student’s seat within that row. Repeat this process until five students

have been identified. (If the classroom is larger, use additional digits so that every student can be sampled.)

Describe how you would use the table of random numbers to take a random sample of size 40 from a large directory consisting of 3041 pages, with 480 lines per page.

Once again, there are many ways. For instance, use the initial 4 digits of each random number (between 0001 and 3041) to identify the page number of the telephone

directory and the next 3 digits (between 001 and 480) to identify the particular line on that page. Repeat this process, using 7-digit numbers, until 40 telephone

numbers have been identified.

Random Assignment

A procedure designed to ensure that each subject has an equal chance of being assigned to any group in an experiment.