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Definition
| measure of variability or measuring the deviation from the mean |
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Term
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Definition
| As the number in the same increases the Sum of all x's across n tends toward normal distribution |
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Term
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Definition
| for any k ge 1, at (1-1/k squared) of the measurements in any set must lie with in k SD of their mean |
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Definition
| closely approximates a normal distribution if n is reasonably large but no more the 20 percent of the total population |
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| 2 measures of variable dependence |
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Definition
1. covariance
2. simple coefficient of linear correlation |
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Term
| coefficient of correlation |
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Definition
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Term
| purpose of sample surveys |
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Definition
| to estimate numerical characteristics called parameters like mean, total, or variance |
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Term
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Definition
object on which a measurement is take
Ex. a registered voter in community |
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Term
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Definition
a collection of elements about which we wish to make an inference
Ex. collection of voters in a community |
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Definition
nonoverlapping collection of elements from the population that covers the entire population
Ex. households |
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Term
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Definition
list of sampling units
Ex. list of all registered voter's households |
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Term
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Definition
| a collection of sampling units drawn from a frame or frames |
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Term
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Definition
| sample designs based on planned randomness |
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Term
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Definition
| selecting a group of n sampling units in a way that each sample of size n has the same chance of being selected |
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Definition
| dividing the population elements into 2 or more groups (strata) and select a simple random sample from each group |
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Definition
| divide the population into groups by simple random sample then sample items within the cluster |
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Definition
| selecting every nth person |
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Definition
| selecting randomly until reach a limit that matches the population (in all determining factors) |
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Term
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Definition
| unclustered directory-assisted, random-digit telephone samples - proportuate stratified sampling design |
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Term
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Definition
| differences in population between unlisted and listed telephone customers systematicly effects survey results of only listed telephone numbers |
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Term
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Definition
-when recorded data deviates from the truth
-by sampling coverage or nonresponse due to interviewer, respondent, instrument, or method of data collection |
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Term
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Definition
| the deviation between an estimate from an ideal sample and the population environment |
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Term
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Definition
| the sampling frame does not matchup perfectly with the target population |
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Term
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Definition
3 ways:
1. inability to contact element
2. inability for respondent to answer
3. refusal to answer |
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Term
| What are the benefits and problems of personal interviews? |
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Definition
benefits: usually answer questions and able to note reaction and eliminate misunderstandings
problems: cost and trained interviewers |
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Term
| What are the benefits of telephone interviews? |
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Definition
interviews can be supervised
less cost
random digit dialing (only 20% of numbers are residential) |
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Term
| Benefits and problems of Self-Administered Questionaires |
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Definition
lowest rate of response
low costs |
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Term
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Definition
| usually not studies with people or using medical records |
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Term
| What are some methods to reduce errors in surveys? |
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Definition
1. Callbacks - use different times
2. rewards to participate - offered only after being randomly selected
3. train interviewers
4. check data
5. carefully planned questionaires |
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Term
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Definition
| the procedure for selecting the sample |
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Term
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Definition
| a type of sampling procedure in which a sample of size n is drawn from a population of size N such that every possible sample of size n has the same chance of being selected |
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Term
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Definition
| seperating the population elements into nonoverlapping groups and then selecting a simple random sample |
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Term
| What are three reasons to stratify? |
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Definition
1. produce a smaller bound on the error of estimation
2. cost
3. to find information about each strata (domain) |
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Term
| What three factors are used to allocate samples when stratifying? |
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Definition
1. total number of elements in each stratum
2. the variability of observations within each stratum
3. the cost of obtaining an observations from each stratum |
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Term
| What are the three methods of stratifying? |
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Definition
1. proprotional
2. Neyman
3. Optimal |
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