Stat 2331 Final Exam Actual Questions and
CORRECT Answers
Getting an adequate amount of sleep can improve a variety of physiological functions, and it
is known that the average number of hours that people sleep each night is Normally
distributed. A psychiatrist at a major research center takes an SRS of 25 emotionally
disturbed patients and records the average amount of sleep that each gets on a typical night.
He summarizes the data and finds that x bar=6.90xˉ=6.90 and s=0.878s=0.878. Suppose a
90% confidence interval for the mean amount of time that emotionally disturbed patients
sleep during a typical night is (6.6, 7.2). Interpret this interval in the context of this problem. -
CORRECT ANSWER We are 90% confident that the mean hours of sleep that
emotionally disturbed patients get on a typical night is in this interval.
Four of the 20 students (20 %) in a class are fraternity or sorority members . A random
sample of 5 students in the class is taken and the number of students in the sample who are
fraternity or sorority members is counted (out of the 5) . Does this constitute a binomial
experiment ? - CORRECT ANSWER No, the probability of success is not constant
from trial to trial
Sample A: 1, 2, 3, 4, 5, 6, 7, 8, 9
Sample B: 1, 2, 3, 4, 5, 6, 7, 8, 100
Which of the following measures of center will be the same for both samples? - CORRECT
ANSWER IQR
Suppose a linear regression equation is ŷ=24.90+0.024x and all the regression conditions are
met. If the R^2 value for this regression model is 0.79, what is the correlation coefficient, R?
- CORRECT ANSWER 0.889
Studies that compare treatments for chronic medical conditions such as headaches can use the
same subjects for each treatment. One such study considered a drug (a pill called
Sumatriptan) for treating migraine headaches in children. The study observed each of 30
children at two times when the child had a migraine headache. They received the drug at one
time and a placebo at the other time. The order of treatment was randomized and the study
was double-blind. For each child, the response was whether the drug or the placebo provided
better pain relief. Of the 30 children, 22 had more pain relief with the drug and 8 had more
pain relief with the placebo. Let p denote the proportion of children having better pain relief
, with the drug, in the population of children who suffer periodically from migraine headaches.
Suppose you want to test the claim that more than half of the population gets better pain relief
with the drug - CORRECT ANSWER There is enough evidence that the true
proportion of children who get better pain relief with the drug is greater than 0.5.
Ten years ago , the mean SAT Math score of all high school students in a small town in Texas
was 490 with a standard deviation of 80. The school administrators want to test their claim
that the mean score has improved . They obtain the SAT Math scores for a SRS of 25 students
from their town , and their mean score is x bar =525. The p-value of their test is 0.019 . Based
on a significance level of α= 0.05 , what decision would the administrators make for their test
? And if they later learn the average SAT Math score of all high school students in their town
is in fact equal to 505 , would their decision be correct or an error ? - CORRECT
ANSWER They would reject the null and make a correct decision
A random sample of 120 recent donations at a blood bank reveals that 90 were Type O blood .
Find the p value to test that the actual percentage of Type O donations is greater than 63 % ,
the proportion of the population having Type O blood - CORRECT ANSWER 0.0032
Brands of ginkgo extract claim to "improve memory and concentration" - CORRECT
ANSWER Experiment: Randomized Design
A psychologist takes a SRS of 100 SMU students to test the claim that the proportion of
students who are unhappy with their weight is different from 0.5. She sets α = 0.01. In her
sample, 67 students say they are unhappy with their weight. What is the p−value for this test?
- CORRECT ANSWER 0.9997
An agricultural researcher claims that the wheat variety A has a lower yield per acre than
variety B - CORRECT ANSWER Confidence Interval for the Mean Difference
A university held a blood pressure screening clinic for its professors . The results are
summarized in the table below by age group and blood pressure level . What is the
probability a randomly selected professor has high blood pressure and is under 50 years old?
- CORRECT ANSWER 51/219
CORRECT Answers
Getting an adequate amount of sleep can improve a variety of physiological functions, and it
is known that the average number of hours that people sleep each night is Normally
distributed. A psychiatrist at a major research center takes an SRS of 25 emotionally
disturbed patients and records the average amount of sleep that each gets on a typical night.
He summarizes the data and finds that x bar=6.90xˉ=6.90 and s=0.878s=0.878. Suppose a
90% confidence interval for the mean amount of time that emotionally disturbed patients
sleep during a typical night is (6.6, 7.2). Interpret this interval in the context of this problem. -
CORRECT ANSWER We are 90% confident that the mean hours of sleep that
emotionally disturbed patients get on a typical night is in this interval.
Four of the 20 students (20 %) in a class are fraternity or sorority members . A random
sample of 5 students in the class is taken and the number of students in the sample who are
fraternity or sorority members is counted (out of the 5) . Does this constitute a binomial
experiment ? - CORRECT ANSWER No, the probability of success is not constant
from trial to trial
Sample A: 1, 2, 3, 4, 5, 6, 7, 8, 9
Sample B: 1, 2, 3, 4, 5, 6, 7, 8, 100
Which of the following measures of center will be the same for both samples? - CORRECT
ANSWER IQR
Suppose a linear regression equation is ŷ=24.90+0.024x and all the regression conditions are
met. If the R^2 value for this regression model is 0.79, what is the correlation coefficient, R?
- CORRECT ANSWER 0.889
Studies that compare treatments for chronic medical conditions such as headaches can use the
same subjects for each treatment. One such study considered a drug (a pill called
Sumatriptan) for treating migraine headaches in children. The study observed each of 30
children at two times when the child had a migraine headache. They received the drug at one
time and a placebo at the other time. The order of treatment was randomized and the study
was double-blind. For each child, the response was whether the drug or the placebo provided
better pain relief. Of the 30 children, 22 had more pain relief with the drug and 8 had more
pain relief with the placebo. Let p denote the proportion of children having better pain relief
, with the drug, in the population of children who suffer periodically from migraine headaches.
Suppose you want to test the claim that more than half of the population gets better pain relief
with the drug - CORRECT ANSWER There is enough evidence that the true
proportion of children who get better pain relief with the drug is greater than 0.5.
Ten years ago , the mean SAT Math score of all high school students in a small town in Texas
was 490 with a standard deviation of 80. The school administrators want to test their claim
that the mean score has improved . They obtain the SAT Math scores for a SRS of 25 students
from their town , and their mean score is x bar =525. The p-value of their test is 0.019 . Based
on a significance level of α= 0.05 , what decision would the administrators make for their test
? And if they later learn the average SAT Math score of all high school students in their town
is in fact equal to 505 , would their decision be correct or an error ? - CORRECT
ANSWER They would reject the null and make a correct decision
A random sample of 120 recent donations at a blood bank reveals that 90 were Type O blood .
Find the p value to test that the actual percentage of Type O donations is greater than 63 % ,
the proportion of the population having Type O blood - CORRECT ANSWER 0.0032
Brands of ginkgo extract claim to "improve memory and concentration" - CORRECT
ANSWER Experiment: Randomized Design
A psychologist takes a SRS of 100 SMU students to test the claim that the proportion of
students who are unhappy with their weight is different from 0.5. She sets α = 0.01. In her
sample, 67 students say they are unhappy with their weight. What is the p−value for this test?
- CORRECT ANSWER 0.9997
An agricultural researcher claims that the wheat variety A has a lower yield per acre than
variety B - CORRECT ANSWER Confidence Interval for the Mean Difference
A university held a blood pressure screening clinic for its professors . The results are
summarized in the table below by age group and blood pressure level . What is the
probability a randomly selected professor has high blood pressure and is under 50 years old?
- CORRECT ANSWER 51/219
