Statistics: Sampling Techniques

Random samples

Answer explanation

are selected by using chance methods or random numbers.

ex random samples

Answer explanation

Number each object in the population; Place the numbered card in a box and mix them; Select as many card as needed to form the sample.

Systematic samples

Answer explanation

Numbering each object in the population; Selecting every Kth value.

ex Systematic samples

Answer explanation

suppose there are 2000 students in an elementary school and a sample of 50 students is needed. Solution: give a number to each student. then find k=2000/50=40 and every 40th student would be selected. Choose randomly the 1st student from 1 through 40.

Stratified samples

Answer explanation

are selected by Divide the population into groups (X { typically: race, age, gender, religion, education}) Obtain a random or systematic sample of each X; Put together the samples obtained in the previous step for your ________.

ex stratified samples

Answer explanation

There are 500 students in a private school in which 350 are male and 150 are female. We need 11 students from each. Solution males k=350/11=31.81 approximately 31 round down. Then randomly choose 1 from 31. then count from that number 31 times till you get 11 students. same goes for females.

Cluster samples

Answer explanation

are selected by Divide the population into sections "often geographical"; Obtain a random or systematic sample of each; Put together the samples obtained in the previous step for your ________.

ex cluster samples

Answer explanation

assume town A has 500 families. In this town there are 20% low income families, 50% middle income families, and 30% upper-income families. We need 30 families from each cluster. Solution .20(500)=100 low income .5(500)=250 middle income .3(500)=150 upper income.

sample

Answer explanation

part of a population

Random, systematic, stratified, cluster

Answer explanation

Name and define the four basic sampling methods.