OPRE 6301 EXAM 1 QUESTIONS AND
ANSWERS 2026 VERIFIED.
Population - ANS is the group of all items of interest to a statistics practitioner.
☞ often of very large size; sometimes even infinite
Sample - ANS is a subset of data drawn from the population.
☞ can be of large size, but smaller than the population
Inferential statistics - ANS a body of methods used to draw conclusions or inferences about
population parameters based on sample statistics.
parameter - ANS ☞ a descriptive measure of a population
Parameter- is a measurement of the population
Ex. The salary of people in Virginia. The salary is the parameter.
statistic - ANS ☞ a descriptive measure of a sample is called a statistic, which is an estimate
for the corresponding population parameter
Non-response bias - ANS occurs, if only a small fraction of the randomly sampled people
choose to respond to a survey.
@2026/2027 ALLRIGHTS RESERVED.
, Voluntary (self-selected) response bias - ANS occurs, when those who respond have strong
opinions on the issue being asked about.
Convenience sample - ANS occurs, when the sample only include individuals who are easily
accessible
Sampling error - ANS refers to difference between the sample and the population that exists
only because of the observations that happened to be selected for the sample.
☞ Commonandintrinsic
☞ Can be reduced only by taking larger sample size
Nonsampling error - ANS results from mistakes made in the acquisition of data or from the
sample observations being selected improperly
☞ Errors in data acquisition.
☞ Nonresponse error.
☞ Selection bias.
Stratified sampling - ANS divide-and-conquer approach- divide the population into strata
then pick randomly from each strata.
• The population is divided into non-intersecting groups called strata.
☞ In the MLB example, the teams could represent the strata.
• A second sampling method (e.g., simple random sampling) is employed within each stratum.
☞ Sample 4players from each team for a total of 120 players.
• We can make inference about the total population, within each stratum, or compare strata
@2026/2027 ALLRIGHTS RESERVED.
ANSWERS 2026 VERIFIED.
Population - ANS is the group of all items of interest to a statistics practitioner.
☞ often of very large size; sometimes even infinite
Sample - ANS is a subset of data drawn from the population.
☞ can be of large size, but smaller than the population
Inferential statistics - ANS a body of methods used to draw conclusions or inferences about
population parameters based on sample statistics.
parameter - ANS ☞ a descriptive measure of a population
Parameter- is a measurement of the population
Ex. The salary of people in Virginia. The salary is the parameter.
statistic - ANS ☞ a descriptive measure of a sample is called a statistic, which is an estimate
for the corresponding population parameter
Non-response bias - ANS occurs, if only a small fraction of the randomly sampled people
choose to respond to a survey.
@2026/2027 ALLRIGHTS RESERVED.
, Voluntary (self-selected) response bias - ANS occurs, when those who respond have strong
opinions on the issue being asked about.
Convenience sample - ANS occurs, when the sample only include individuals who are easily
accessible
Sampling error - ANS refers to difference between the sample and the population that exists
only because of the observations that happened to be selected for the sample.
☞ Commonandintrinsic
☞ Can be reduced only by taking larger sample size
Nonsampling error - ANS results from mistakes made in the acquisition of data or from the
sample observations being selected improperly
☞ Errors in data acquisition.
☞ Nonresponse error.
☞ Selection bias.
Stratified sampling - ANS divide-and-conquer approach- divide the population into strata
then pick randomly from each strata.
• The population is divided into non-intersecting groups called strata.
☞ In the MLB example, the teams could represent the strata.
• A second sampling method (e.g., simple random sampling) is employed within each stratum.
☞ Sample 4players from each team for a total of 120 players.
• We can make inference about the total population, within each stratum, or compare strata
@2026/2027 ALLRIGHTS RESERVED.
