Download MORE EXTRA QUESTIONS Here`s some additional test 2 prep

MORE EXTRA QUESTIONS
Here’s some additional test 2 prep questions. Some answers are on the last page.
(1) Sickle-cell disease is a painful disorder of the red blood cells that in the United States
affects mostly African-Americans. To investigate whether the drug hydroxyurea can reduce the pain associated with sickle-cell disease, a study by the NIH gave the drug to
150 sickle-cell sufferers and a placebo to another 150. The researchers then counted the
number of episodes of pain reported by each subject. What is the response variable in
this study?
(2) An experiment was conducted and the results involving the effect of a particular experimental variable was widely reported. Later a critic commented that, in fact, nothing could
usefully be learned from the study because the observed effect was confounded. What
did the critic mean by this?
(3) A medicine to remove the redness in eyes was tested in a group of 100 students. Each
student took either the medicine or a placebo in both eyes. THe specific treatment for
each student was decided by flipping a coin. The participants in the study did not know if
heads or tails resulted in the medication. Identify the basic principles of statistical design
used in this experiment.
Use the following to answer the next four questions:
A call-in poll conducted by USA Today concluded that Americans love Donald Trump. This
conclusion was based on data collected from 7800 calls made by USA Today readers.
(4) What sampling technique is being used?
(5) USA Today reported that of the 7800 calls, 6435 calls were supportive of Donald Trump.
This results in a percentage of 82.5%. Of the 6435 supportive calls, about half came from
female callers. Which values can be labelled as statistic(s)?
(6) USA Today later reported that 5640 of the 7800 calls for the poll came from the offices
owned by one man, Cincinatti financier Carl Lindner, who is a friend of Donald Trump.
What can we conclude about the results of this poll?
(7) Excluding the previous question, what do you think about the design or accuracy of this
survey?
Use the following to answer the next five questions:
If you draw an M&M candy at random from a bag of the candies, the candy you draw will
have one of six colours. The probability of drawing each colour depends on the proportion
of each colour among all candies made. Assume the table below gives the probabilities
for the colour of a random chosen M&M:
Colour
Brown Red Yellow Greed Orange Blue
Probability
0.3
0.3
?
0.1
0.1
0.1
(8) What is the probability of drawing a yellow candy?
(9) What is the probability of not drawing a red candy?
(10) What is the probability that you draw neither a brown nor a green candy?
(11) If you select two M&M’s and their colours are independent, then what is the probability
that they are both the same colour? (HARDER)
(12) What do you think of the assumption of independence in the above question?
Use the following to answer the next two questions:
Let the random variable X represent the profit made on a randomly selected day by a
small clothing store on Main Street. Assume that X is normal, with a mean of $360 and
a standard deviation of $50.
(13) What is P (X > $400)?
(14) The probability that on a randomly selected dat the store will make less than this amount
is approximately 60%.
Use the following to answer the next four questions:
Suppose that a college determines the following distribution for X = number of courses
taken by a full-time student this semester:
Value of X
3
4
5
6
Probability 0.07 ? 0.25 0.28
(15) What is the probability that X = 4?
(16) What is the average number of courses full-time students at this college take this semester?
(17) What is the standard deviation of the number of courses full-time students at this college
take this semester?
(18) What is P (X > 4.74)?
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
(15)
(16)
(17)
(18)
ANSWERS (not solutions...):
The number of episodes of pain.
...
Control, randomization, repetition.
Volunteer sampling.
6435, 82.5%, 50%.
Biased, overstating popularity.
...
0.1
0.7
0.6
0.22
...
0.2119
$372.60
0.40
4.74
0.94
0.53