1.3 Simple Random Sampling

Random sampling

-using chance to select individuals from a population to be included in the sample.

Steps for Obtaining a Simple Random Sample

1) Obtain a frame that lists all the individuals in the population of interest. Number the individuals in the frame 1 - N. 2) Use a random number table, graphing calculator, or statistical software to randomly generate n numbers where n is the desired sample size.

simple random sample

A sample of size n selected from the population each possible sample of size n has an equal chance of being selected.

simple random sampling

A sampling procedure in which each member of the population has an equal probability of being included in the sample.

435 members in the House of Representatives. Explain how to conduct a simple random sample of 5 members Step 3

Match the generated random numbers to the corresponding Representatives

Step 1 for Obtaining a Simple Random Sample

Obtain a frame that lists all the individuals in the population of interest. Number the individuals in the frame 1 - N.

435 members in the House of Representatives. Explain how to conduct a simple random sample of 5 members Step 1

Put the members in alphabetical order. Number the members from 1 to 435.

435 members in the House of Representatives. Explain how to conduct a simple random sample of 5 members Step 2

Randomly select five numbers using a random number generator. First, set the seed. The seed is an initial point for the generator to start creating random numbers—like selecting the initial point in the table of random numbers. The seed can be any nonzero number. Then generate the random numbers.

Step 2 for Obtaining a Simple Random Sample

Use a random number table, graphing calculator, or statistical software to randomly generate n numbers where n is the desired sample size.

If convenience is used to obtain a sample

the results of the survey are meaningless

Suppose a study group consists of 5 students: Bob, Patricia, Mike, Jan, and Maria 2 of the students must go to the board to demonstrate a homework problem. List all possible samples of size 2 (without replacement).

•Bob, Patricia •Bob, Mike •Bob, Jan •Bob, Maria •Patricia, Mike