Question | Answer |
Population | an entire group of persons or elements that have at least one thing in common |
Sample | a small group of persons or elements selected from the total population |
Random sampling | Random sampling is where each member of the sample is randomly selected from the population |
Sampling bias | Sampling bias is caused by systematic errors in the sampling process. |
Sample size | In general, the larger the sample size, the more representative it is of the population |
bias | unfair - results favoring one group over another |
biased sampling | a sample that over or underrepresents a portion of the population |
Representative | The data collected should represent the whole population, not just a small piece or an extreme. |
The problem with collecting the sample water from the part of the lake nearest to the stream that runs into the lake. | Not representative |
The problem with evaluating an ice cream sundae by selecting one of the peanuts and reporting on it. | Not representative, not a good cross-section of the population |
The problem with evaluating traffic at a location by watching it from 7 to 8 a.m. | Not representative since it is not a cross-section over a long enough period of time. Traffic at that one time may be unlike the typical situation. |
The problem with picking a new school song by surveying the choir. | Not representative. It likely that the choir is made up of students with similar interest that may or may not be a good cross-section of the school. |
The problem with evaluating the quality of the candy a factory by checking either the first or last batches produced. | Not representative. Not random. First and last bachtes may be unlike candy produced in between. |
The problem with evaluating a high school by sureying 5 students. | Sample is not large enough |
The problem with gathering data by posting a survey on a web page. | Sample will only consist of those with computer access. People could potentially skew the results by filling out multiple surveys. |
The problem with evaluating a teacher by gathering data the first 5 minutes of 20 lessons. | Sample does not represent the end or middle of the lessons. |