Exam (elaborations)
STA 270 EXAM QUESTIONS AND VERIFIED ANSWERS
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STA 270 EXAM QUESTIONS AND VERIFIED ANSWERS...
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z scores - ANSWERState whether the data are best described as a population or a sample.
The U.S. Department of Transportation announces that of the 250
million registered passenger vehicles in the US, 2.1% are electro-gas
hybrids. - ANSWER Population
The population is all trees in a forest. We walk through the forest and
pick out trees that appear to be representative of all the trees in the
forest.
State whether or not the sampling method described produces a random
sample from the given population. - ANSWER Not Random
Indicate whether we should trust the results of the following study. Is the
method of data collection biased?
Ask a random sample of students at the library on a Friday night "How
many hours a week do you study?" to collect data to estimate the
average number of hours a week that all college students study. -
ANSWER Biased
The website fox6now.com held an online poll in June 2015 asking "What
do you think about the concept of having an everyday uniform for work,
like Steve Jobs did?" Of the people who answered the question, 24%
said they loved the idea, 58% said they hated the idea, and 18% said
that they already wore a uniform to work.
,(a) Are the people who answered the poll likely to be representative of
all adult workers?
b) Is it reasonable to generalize this result and estimate that 24% of all
adult workers would like to wear a uniform to work? - ANSWER a) NO
b)NO
In July 2015, a poll asked a random sample of 1236 registered voters in
Iowa whether they agree or disagree that the world needs to do more to
combat climate change.1 The results show that 65% agree, while 25%
disagree and 10% don't know.
(a) Is the sample likely to be representative of all registered voters in
Iowa?
(b) Is it reasonable to generalize this result and estimate that 65% of all
registered voters in Iowa agree that the world needs to do more to
combat climate change? - ANSWER a)YES
b)YES
randomized comparative experiment - ANSWER an experiment that
uses both comparison of two or more treatments and random
assignment of subjects to treatments
matched pairs experiment - ANSWER two groups, each get both
treatments nut in a random order
State whether the following claim is one of association and causation,
association only, or neither association nor causation.
Daily exercise improves mental performance. - ANSWER association
with causation
State whether the following claim is one of association and causation,
association only, or neither association nor causation.
Cell phone radiation leads to deaths in honey bees. - ANSWER
association with causation
, State whether the following claim is one of association and causation,
association only, or neither association nor causation.
Cat owners tend to be more educated than dog owners. - ANSWER
Association
Is the following an experiment or an observational study?
To examine whether eating brown rice affects metabolism, we ask a
random sample of people whether they eat brown rice and we also
measure their metabolism rate. - ANSWER observational, since nothing
is being manipulated only observed and then recorded
Is the following an experiment or an observational study?
To examine whether planting trees reduces air pollution, we find a
sample of city blocks with similar levels of air pollution and we then plant
trees in half of the blocks in the sample. After waiting an appropriate
amount of time, we measure air pollution levels. - ANSWER experiment,
since they are manipulating where to and not plant trees
Do the following data come from an experiment or an observational
study?
A gene called ACTN3 encodes a protein which functions in fast-twitch
muscles. Some people have a variant of this gene that cannot yield this
protein. (So we might call the gene variant a possible non-sprinting
gene.) To address the question of whether this gene is associated with
sprinting ability, geneticists tested people from three different groups:
world-class sprinters, world-class marathon runners, and a control group
of non-athletes. In the samples tested, 6% of the sprinters had the gene
variant, compared with 18% of the non-athletes and 24% of the
marathon runners. This study1 suggests that sprinters are less likely
than non-sprinters to have the gene variant. - ANSWER observational,
since they can manipulate the gene
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