Stratified Sampling
Is obtained by separating the population into nonoverlapping groups called strata and then obtaining a simple random sample from each stratum. The individuals within each stratum should be homogenous or similar in some way.
Systematic sampling
is obtained by selecting every kth individual from the population. The first individual selected corresponds to a random number between 1 and k.
Systemic sampling
1. If possible approximate the sampling size N.2. Determine the sampling size desired n.3. Compute N/n and round down to the nearest integer. This value is k.4.Randomly select a number between 1 and k. Call this number p.5. The sample will consist of the following individuals: p,p + k, p + 2k....... p+(n-1)kSuppose N= 20,325 and we desire a sample size of n=100. Divide 20,325/100=203.25 so k= 203. Randomly chose that we start with the 90th individual 90+ 203.... 90,293,496... the last number will be 1 less then the sample size which is 99 times k which is 203 added to the starting value which is 90 which equals 20,187 which is the last individual in the survey.
Cluster Sample
Is obtained by selecting all individuals within a randomly selected collection or group of individuals.
Convience sampling
is a sample in which the individuals are easily obtained and not based on randomness.
Which sampling method does not require a frame?
Systematic
Which sample type?
A(n) cluster sample is obtained by dividing the population into groups and selecting all individuals from within a random sample of the groups.
Which sample type?
A(n) stratified sample is obtained by dividing the population into homogeneous groups and randomly selecting individuals from each group.
To estimate the percentage of defects in a recent manufacturing batch, a quality control manager at Daimler minus Chrysler selects every 13th van that comes off the assembly line starting with the sixth until she obtains a sample of 80 vans.
Systematic
To determine customer opinion of their pricing, Greyhound Lines randomly selects 120 busses during a certain week and surveys all passengers on the busses.
Cluster
IBM wants to administer a satisfaction survey to its current customers. Using their customer database, the company randomly selects 60 customers and asks them about their level of satisfaction with the company.
Simple random
A internet site asks its members to call in their opinion regarding their web searching habits.
Convenience
A salesperson obtained a systematic sample of size 25 from a list of 500 clients. To do so, he randomly selected a number from 1 to 20, obtaining the number 13. He included in the sample the 13th client on the list and every 20th client thereafter. List the numbers that correspond to the 25 clients selected.
13,33......493
To determine her air quality, Carolyn divides up her day into three parts: morning, afternoon, and evening. She then measures her air quality at 2 randomly selected times during each part of the day.
Stratified
The human resource department at a certain company wants to conduct a survey regarding worker benefits. The department has an alphabetical list of all 5585 employees at the company and wants to conduct a systematic sample of size 60.
(a) What is k? k=93(b) Determine the individuals who will be administered the survey. Randomly select a number from 1 to k. Suppose that we randomly select 18. Starting with the first individual selected, the individuals in the survey will be 18, 111,204.....550