PSTAT 5LS UCSB final UPDATED
ACTUAL Exam Questions and CORRECT
Answers
data - CORRECT ANSWER - collection of observations (e.g. measurements, survey
responses)
population - CORRECT ANSWER - -Complete collection of all of the data of interest
-In many cases the population conceptual (e.g. daily yields of a power plant for next 2 years
-In most cases measuring the whole population is too costly, unnecessary or impossible
-The entire group of individuals in which we are interestedbut can't usually assess directly
sample - CORRECT ANSWER - -Subset of the population
-a subset of measurements selected from the population of interest
-should be representative of the population
-could be the whole population (e.g. US Census in ideal situations)
-many possible samples when sample is a subset of the whole population
-The part of the population we actually examine and for which we do have data
parameter - CORRECT ANSWER - -is a number summarizing a characteristic of the
population
-A numerical measure describing a
population characteristic
statistic - CORRECT ANSWER - -is a number summarizing a characteristic of a sample
-A numerical measure describing a samplecharacteristic
,statistical inference - CORRECT ANSWER - makes use of information from a sample to
draw conclusions about the population from which the sample was taken
inference process - CORRECT ANSWER - Step 1: What is the QUESTION of interest?
Step 2: What POPULATION is associated with the
QUESTION?
Step 3: Take a SAMPLE from the POPULATION.
Step 4: Measure one or more VARIABLES on each unit in the Sample.
Step 5: Make a SUMMARY of all Sample Data obtained on the VARIABLES.
Step 6: Make an INFERENCE about the POPULATION from the Sample Summary.
context - CORRECT ANSWER - -What do the values represent?
-Where did the data come from?
-Why were they collected?
-An understanding of the context will directly affect the statistical procedure used.
source of data - CORRECT ANSWER - -Is the source objective?
-Is the source biased?
-Is there some incentive to distort or spin results to support some self-serving position?
-Is there something to gain or lose by distorting results?
-Be vigilant and skeptical of studies from sources that may be biased.
sampling method? - CORRECT ANSWER - -Does the method chosen greatly influence
the validity of the conclusion?
-Voluntary response (or convenience) samples often have bias (those with special interest are
more likely to participate or sample is not representative of the population). These samples'
results are not necessarily valid.
-The gold standard is random sampling.
,the best sampling method (good sampling method) - CORRECT ANSWER - random
sampling
conclusion and practical implications - CORRECT ANSWER - -Make statements that are
clear to those without an understanding of statistics and its terminology.
-Avoid making statements not justified by the statistical analysis.
-State practical implications of the results.
-There may exist some statistical significance yet
there may be NO practical significance.
-Common sense might suggest that the finding does not make enough of a difference to justify its
use or to be practical.
the 2 types of data - CORRECT ANSWER - 1.) categorical (nominal or ordinal)
2.) quantitative (discrete or continuous)
categorical data - CORRECT ANSWER - -Something that falls into one of several
categories.
-We can then report the count or proportion of individuals in each category.
1.) Nominal: unordered (For example, hair color, blood type, gender, make of car)
2.) Ordinal: ordered (For example, letter grades A, B, C, D, and F; service ratings excellent, very
good, good, fair and poor)
quantitative data - CORRECT ANSWER - -Take numerical values for which arithmetic
operations such as adding and averaging make sense.
1.) Discrete if it can assume only a finite or countable number of values.
2.) Continuous if it can assume the infinitely many values corresponding to the points on a line
interval.
observational study - CORRECT ANSWER - -Record data on individuals without
attempting to influence the responses
, -Cannot conduct randomized experiments (ethical reasons or physically impossible)
-May provide evidence to suggest or support causal theories that can be tested using subsequent
experiment or with other research
-Causation is not always a goal of analysis
observational study example - CORRECT ANSWER - In 1992, several major medical
organizations said that women should take hormones such as estrogen after menopause, when
natural production of these hormones ends. Indeed, women who had taken hormones seemed to
reduce their risk of a heart attack by 35% - 50%.
experiment - CORRECT ANSWER - Deliberately impose a treatment on individuals, and
record their responses. Influential factors can be controlled. Individuals do not chose which
treatment they get
experiment example - CORRECT ANSWER - By 2002, several studies with women of
different ages concluded that hormone replacement does not reduce the risk of heart attacks.
These studies had assigned women to either hormone replacement or to dummy pills that look
and taste the same as the hormone pills. The assignment was done by a coin toss, so that each
woman was equally likely to get either pill.
confounding - CORRECT ANSWER - -Two variables are confounded when their effects
on a response variable cannot be distinguished
-Observational studies often fail to yield clear causal conclusions, because the explanatory
variable is confounded with lurking variables.
sampling design - CORRECT ANSWER - how to draw a sample from the population
random sampling - CORRECT ANSWER - members from the population are selected in
such a way that each individual member in the population has an equal chance of being selected (
ex. Draw from a hat (lottery style), Flip a coin, Use software that generates random numbers)
poor sampling methods - CORRECT ANSWER - -convenience sampling
ACTUAL Exam Questions and CORRECT
Answers
data - CORRECT ANSWER - collection of observations (e.g. measurements, survey
responses)
population - CORRECT ANSWER - -Complete collection of all of the data of interest
-In many cases the population conceptual (e.g. daily yields of a power plant for next 2 years
-In most cases measuring the whole population is too costly, unnecessary or impossible
-The entire group of individuals in which we are interestedbut can't usually assess directly
sample - CORRECT ANSWER - -Subset of the population
-a subset of measurements selected from the population of interest
-should be representative of the population
-could be the whole population (e.g. US Census in ideal situations)
-many possible samples when sample is a subset of the whole population
-The part of the population we actually examine and for which we do have data
parameter - CORRECT ANSWER - -is a number summarizing a characteristic of the
population
-A numerical measure describing a
population characteristic
statistic - CORRECT ANSWER - -is a number summarizing a characteristic of a sample
-A numerical measure describing a samplecharacteristic
,statistical inference - CORRECT ANSWER - makes use of information from a sample to
draw conclusions about the population from which the sample was taken
inference process - CORRECT ANSWER - Step 1: What is the QUESTION of interest?
Step 2: What POPULATION is associated with the
QUESTION?
Step 3: Take a SAMPLE from the POPULATION.
Step 4: Measure one or more VARIABLES on each unit in the Sample.
Step 5: Make a SUMMARY of all Sample Data obtained on the VARIABLES.
Step 6: Make an INFERENCE about the POPULATION from the Sample Summary.
context - CORRECT ANSWER - -What do the values represent?
-Where did the data come from?
-Why were they collected?
-An understanding of the context will directly affect the statistical procedure used.
source of data - CORRECT ANSWER - -Is the source objective?
-Is the source biased?
-Is there some incentive to distort or spin results to support some self-serving position?
-Is there something to gain or lose by distorting results?
-Be vigilant and skeptical of studies from sources that may be biased.
sampling method? - CORRECT ANSWER - -Does the method chosen greatly influence
the validity of the conclusion?
-Voluntary response (or convenience) samples often have bias (those with special interest are
more likely to participate or sample is not representative of the population). These samples'
results are not necessarily valid.
-The gold standard is random sampling.
,the best sampling method (good sampling method) - CORRECT ANSWER - random
sampling
conclusion and practical implications - CORRECT ANSWER - -Make statements that are
clear to those without an understanding of statistics and its terminology.
-Avoid making statements not justified by the statistical analysis.
-State practical implications of the results.
-There may exist some statistical significance yet
there may be NO practical significance.
-Common sense might suggest that the finding does not make enough of a difference to justify its
use or to be practical.
the 2 types of data - CORRECT ANSWER - 1.) categorical (nominal or ordinal)
2.) quantitative (discrete or continuous)
categorical data - CORRECT ANSWER - -Something that falls into one of several
categories.
-We can then report the count or proportion of individuals in each category.
1.) Nominal: unordered (For example, hair color, blood type, gender, make of car)
2.) Ordinal: ordered (For example, letter grades A, B, C, D, and F; service ratings excellent, very
good, good, fair and poor)
quantitative data - CORRECT ANSWER - -Take numerical values for which arithmetic
operations such as adding and averaging make sense.
1.) Discrete if it can assume only a finite or countable number of values.
2.) Continuous if it can assume the infinitely many values corresponding to the points on a line
interval.
observational study - CORRECT ANSWER - -Record data on individuals without
attempting to influence the responses
, -Cannot conduct randomized experiments (ethical reasons or physically impossible)
-May provide evidence to suggest or support causal theories that can be tested using subsequent
experiment or with other research
-Causation is not always a goal of analysis
observational study example - CORRECT ANSWER - In 1992, several major medical
organizations said that women should take hormones such as estrogen after menopause, when
natural production of these hormones ends. Indeed, women who had taken hormones seemed to
reduce their risk of a heart attack by 35% - 50%.
experiment - CORRECT ANSWER - Deliberately impose a treatment on individuals, and
record their responses. Influential factors can be controlled. Individuals do not chose which
treatment they get
experiment example - CORRECT ANSWER - By 2002, several studies with women of
different ages concluded that hormone replacement does not reduce the risk of heart attacks.
These studies had assigned women to either hormone replacement or to dummy pills that look
and taste the same as the hormone pills. The assignment was done by a coin toss, so that each
woman was equally likely to get either pill.
confounding - CORRECT ANSWER - -Two variables are confounded when their effects
on a response variable cannot be distinguished
-Observational studies often fail to yield clear causal conclusions, because the explanatory
variable is confounded with lurking variables.
sampling design - CORRECT ANSWER - how to draw a sample from the population
random sampling - CORRECT ANSWER - members from the population are selected in
such a way that each individual member in the population has an equal chance of being selected (
ex. Draw from a hat (lottery style), Flip a coin, Use software that generates random numbers)
poor sampling methods - CORRECT ANSWER - -convenience sampling
