Exam 2 Flashcards
What is a population?
the entire set people data or things that is the subject of exploration
What is a census?
data is
collected from each
member of a population
What is a parameter?
a characteristic or
measure of a population
What is a statistic?
a characteristic or
measure of a sample
What is a sampling error?
the difference between
results obtained from a
sample and those that
would have been
obtained from the
population
What is a sampling plan?
process of selecting
the people (or objects) to be surveyed
What is a non probability sample?
-A sample that relies on
personal judgment in the
element selection process
-Sampling error cannot be
estimated or calculated
- Results should not be used to
make inferences about the
population
what is a probability sample?
A sample in which each
target population element
has a known, nonzero
chance of being included in
the sample
What are the techniques for a non probability sample?
1.Convenience
2. Judgment
o Snowball
3.Quota
What are the probability sample techniques?
- Simple Random
2.Systematic - Stratified
Cluster - Area
What is convenience technique?
population are sampled simpley because they are in the right place at the right time.
What is judgement technique?
Population elements are handpicked by the researcher because they are expected to serve the research purpose. Ex interviewing knowledgeable people.
What is the snowball technique
What is the qouta technique?
You know how the population is divided up. Ex 30% of all students are seniors so you choose to interview 30 seniors out of 100 interviews.
What is the simple random technique?
each member of the population has an equal chance of being selected.
What is the systematic technique?
sample where every __th element is selected. Ex every 20th student will be selected.
What is the stratified technique?
pulling people homogenous from the strata. Example you could chose age.
What is the cluster technique?
researchers divide a population into smaller groups known as clusters. They then randomly select among these cluster
What is the area technique?
Are results from a nonprobability sample generalizable?
No
Are results from a probability sample generalizable?
Yes.
what are the three basic factors that impact the size of sample needed?
- amount of diversity needed
- amount of percision needed
- degree of confidence (confidence interval increases as sample size increases)
does the size of the population have bearing on the size of the sample?
Size of the population has no bearing on the size of the
sample
does the size of the population have bearing on the size of the sample?
Size of the population has no bearing on the size of the
sample
What is the relationship between population elements and the size of the population?
The more similar the population elements, the few people
needed regardless of how large the population is
What are the other considerations in determining sample size?
- Budget
- Type of analysis being conducted
- past research
what do sample statistics allow?
Sample statistics allow
Inferences about Population
Parameters
What is selecting the sample procedure for nonprobability sample?
Sampling error cannot be
estimated or calculated
Inferences cannot be made
about the population
Inferences are limited to
the sample
What is selecting the sample procedure for probability sample?
One can statistically assess
level of sampling error
Inferences can be made
about the population, and
not just the sample
Inferences are not limited
to the sample
what is sampling error?
The difference between results obtained from a sample and
results that would have been obtained had information been
gathered from or about every member of the population
what is sampling error?
what are the types of non sampling erros?
- non observation errors
- observation errors
what are the types of non observation errors?
- non coverage errors
- non response errors
What are the types of observation errors?
- response errors
- office errors
What are the types of observation errors?
- response errors
- office errors
What is a noncoverage error?
-Error that arises because of a failure to include some units, or
entire sections, of the defined target population in the sampling
frame
-Noncoverage error is basically a sampling frame problem
How can you reduce noncoverage error?
Can be reduced, although not necessarily eliminated, by recognizing its existence and working to improve the sampling
frame
What is response error?
- Error that represents a failure to obtain information from some elements of the population that were selected and designated
for the sample
-This is a potential problem that only occurs when those who do respond are systematically different in some important way
from those who don’t respond
What is an example of non response error?
-Example – A university wants to assess the success of its graduates,
based on their annual salaries, five years after graduation
-Which graduates are more likely (less likely) to return their survey?
Those who are happy (unhappy) with their salaries.
what are refusals in non response error?
error that arises because some respondents refuse to participate
What is not at homes error?
-error that arises because respondents are not at home when the interviewer calls.
-3-4 call backs required to reach 75% of sample pool
-call backs should be for different days/ times relative to the orignal call
When does response error occur?
Response error occurs when an individual provides a response to
an item, but the response is inaccurate for some reason
What are some possible causes for response error?
Does the respondent understand the question?
Does the respondent know the answer to the question?
Is the respondent willing to provide the true answer to the question?
Is the wording of the question or the situation in which it is asked likely to
bias the response?
What is office error?
Errors that arise in the editing, coding, or analysis phases of
research
How can you reduce office errors?
Most office errors can be reduced, if not eliminated, by
exercising proper controls in data processing
What is response rate?
It is the number of completed interviews with responding units
divided by the number of eligible responding units in the sample
o It serves as an indicator of the overall quality of a data collection effort
o It also provides insight into the likely influence of nonresponse error on the
project
True or false. Researchers must strive to obtain the highest response rates possible in a given situation?
True.
What is the general response rate calculation?
RR=CI/E
RR=response rate
CI= number of completed interviews with responding units
E= Number of eligible responding units in the sample
An online retailer decided to conduct an online survey:
-1000 customers are randomly selected to recieve a survey by email
-202 customers complete the survey
-58 emails are no longer valid
RR=202/(1000-58)= 21%
A researcher calls 200 potential respondents
-112 interviews are completed successfully
-27 people refuse
-57 people cannot be reached
RR=112/(112+27+57)=57%
How do you improve response rates?
-reducing survey length
- guarantee of cinfidentiality or anyomity
- interviewer characteristics and training
- personalization
- response incentives
- follow up surveys
How do you prep data for analysis?
- editing
- coding
3 cleaning the data - handling missing data
What is editing?
The inspection and correction of data to make certain that data meets minimum quality standards
What is coding?
the process of transforming raw data into symbols that can be utilized for analysis.
What is cleaning the data?
Blunders: an error that arisses during coding or data entry.
How do you handle missing data?
- eliminate the case with missing items from further analysis
- substitute values for missing items
- contact the respondent again
What is univariate analsyis?
analysis involving 1 variable
what is multivariate analysis?
analysis invovling multiple variables
What is fequency analysis?
a count of the number of cases that fall into each of the categories. Example gender split.
When are percentages very useful?
interpreting the results of categorial analyses.
What is valid percentages?
Percentages after taking out cases with missing data.
What are the uses for frequency analysis?
-communicate the results of the study via univariate categorial analysis
- determine the degree of item non response
- identify blunders
- identify outliers
What is sampling error?
the difference
between results
obtained from a
sample and those
that would have
been obtained
from the
population
What is sampling error?
the difference
between results
obtained from a
sample and those
that would have
been obtained
from the
population
What is confidence interval?
A projection of the range within which a population
parameter will lie at a given level of confidence based on
a statistic obtained from a probabilistic sample
To produce a confidence interaval we first need to calculate ____?
sampling erorr
What are descrptive statistics?
statistics that describe the distribution of responses on a variable. Most common descrptive statistics are mean and standard deviation.
What does standard deviation measure?
Measure of dispertion. If all respndents are the same than standard deviation is small. IF responses are very high than standard deviation is high
What is confidence interval for means?
A projection of the range within which a population mean
will lie at a given level of confidence
What is Null Hypothesis (H0)
The hypothesis that a proposed
result is not true for the population
What is alternative hypothesis (h1)
The hypothesis that a
proposed result is true for the population
Why conduct multivariate analysis?
- Multivariate analyses allow researchers a closer look at
their data than is possible with univariate analyses - Univariate analyses provide insights about the data while
multivariate analyses can often provide further
illumination of those insights
What is the researcher trying to determine in multivariate analysis?
wheterh one variable has influence over another
When to you fail to reject the null hypothesis?
if the p-value is
GREATER than your alpha (a) (.05)
What is cross tabulation?
A multivariate technique used for studying the
relationship between two or more categorical
variables
what is the pearson product moment correlation coefficient?
It assesses the degree to which the two variables change
consistently across cases
What is a T-test
A t-test is used to compare a continuous measure across
groups.
