ECON 261 EXAM 3 || WITH ERRORLESS ANSWERS.
What can teachers do to alleviate statistics anxiety in their students? To explore this question,
statistics anxiety for students in two classes was compared. In one class, the instructor lectured in
a formal manner, including dressing formally. In the other, the instructor was less formal, dressed
informally, was more personal, used humor, and called on students by their first names. Anxiety
was measured using a questionnaire. Higher scores indicate a greater level of anxiety. The mean
anxiety score for students in the foral lecture class was 25.40. In the informal class, the mean was
20.41. Classify 25.40 and 20.41 as parameters or statistics. correct answers Both 25.40 and 20.41
are statistics.
Almost all medical schools in the United States require students to take the Medical College
Admission Test (MCAT). To estimate the mean score μ of those who took the MCAT on your
campus, you will obtain the scores of an SRS of students. The scores follow a Normal
distribution, and from published information you know that the standard deviation is 10.4.
Suppose that (unknown to you) the mean score of those taking the MCAT on your campus is
500(or 495).
A) If you choose one student at random, what is the probability that the student's score is
between 495 and 505(or 490 and 500)?
B) You sample 25 students. What is the standard deviation of the sampling distribution of their
average score ¯x?
C) What is the probability that the mean score of your sample is between 495 and 505(or 490 and
500)? correct answers A) 0.3688
B) 2.08
C) 0.9836
(for the numbers in parentheses in part A and C, the answers are the same despite the different
values)
There is a new idea for treating advanced melanoma, the most serious kind of skin cancer—
genetically engineer white blood cells to better recognize and destroy cancer cells, then infuse
these cells into patients. The subjects in a small initial study of this approach were 11 patients
whose melanoma had not responded to existing treatments. One outcome of this experiment was
measured by a test for the presence of cells that trigger an immune response in the body and so
, may help fight cancer. The mean counts of active cells per 100,000 cells for the 11 subjects were
3.8 before infusion and 160.2 after infusion.
Are the numbers 3.8 and 160.2 parameters or statistics? correct answers Both 3.8 and 160.2 are
statistics
Florida played a key role in recent presidential elections. Voter registration records in August
2016 show that 38% of Florida voters are registered as Democrats and 36% as Republicans.
(Most of the others did not choose a party.) In September 2016 you used a random digit dialing
device to poll voters for the 2016 presidential elections. You used it to call 250 randomly chosen
residential telephones in Florida. Of the registered voters contacted, 35% are registered
Democrats.
Is each of the numbers that are listed as percentages a parameter or a statistic? correct answers
38% and 36% are parameteers, and 35% is a statistic
Asked what the central limit theorem says, a student replies, "As you take larger and larger
samples from a population, the histogram of the sample values looks more and more Normal."
Is the student right? Explain your answer. correct answers No. The central limit theorem says
nothing about the histogram of the sample values. It deals only with the distribution of the
sample means.
The sampling distribution of a statistic is: correct answers The distribution of values taken by a
statistic in all possible samples of the same size from the same population
A statistic is said to be unbaised if: correct answers the mean of its sampling distribution is equal
to the true value of the parameter being estimated
Scores on the Critical Reading part of the SAT exam in a recent year were roughly Normal with
mean 495 and standard deviation 118. You choose an SRS of 100 students and average their SAT
Critical Reading scores. If you do this many times, the mean of the average scores you get will
be close to correct answers 495.
Scores on the Critical Reading part of the SAT exam in a recent year were roughly Normal with
mean 495 and standard deviation 118. You choose an SRS of 100 students and average their SAT
What can teachers do to alleviate statistics anxiety in their students? To explore this question,
statistics anxiety for students in two classes was compared. In one class, the instructor lectured in
a formal manner, including dressing formally. In the other, the instructor was less formal, dressed
informally, was more personal, used humor, and called on students by their first names. Anxiety
was measured using a questionnaire. Higher scores indicate a greater level of anxiety. The mean
anxiety score for students in the foral lecture class was 25.40. In the informal class, the mean was
20.41. Classify 25.40 and 20.41 as parameters or statistics. correct answers Both 25.40 and 20.41
are statistics.
Almost all medical schools in the United States require students to take the Medical College
Admission Test (MCAT). To estimate the mean score μ of those who took the MCAT on your
campus, you will obtain the scores of an SRS of students. The scores follow a Normal
distribution, and from published information you know that the standard deviation is 10.4.
Suppose that (unknown to you) the mean score of those taking the MCAT on your campus is
500(or 495).
A) If you choose one student at random, what is the probability that the student's score is
between 495 and 505(or 490 and 500)?
B) You sample 25 students. What is the standard deviation of the sampling distribution of their
average score ¯x?
C) What is the probability that the mean score of your sample is between 495 and 505(or 490 and
500)? correct answers A) 0.3688
B) 2.08
C) 0.9836
(for the numbers in parentheses in part A and C, the answers are the same despite the different
values)
There is a new idea for treating advanced melanoma, the most serious kind of skin cancer—
genetically engineer white blood cells to better recognize and destroy cancer cells, then infuse
these cells into patients. The subjects in a small initial study of this approach were 11 patients
whose melanoma had not responded to existing treatments. One outcome of this experiment was
measured by a test for the presence of cells that trigger an immune response in the body and so
, may help fight cancer. The mean counts of active cells per 100,000 cells for the 11 subjects were
3.8 before infusion and 160.2 after infusion.
Are the numbers 3.8 and 160.2 parameters or statistics? correct answers Both 3.8 and 160.2 are
statistics
Florida played a key role in recent presidential elections. Voter registration records in August
2016 show that 38% of Florida voters are registered as Democrats and 36% as Republicans.
(Most of the others did not choose a party.) In September 2016 you used a random digit dialing
device to poll voters for the 2016 presidential elections. You used it to call 250 randomly chosen
residential telephones in Florida. Of the registered voters contacted, 35% are registered
Democrats.
Is each of the numbers that are listed as percentages a parameter or a statistic? correct answers
38% and 36% are parameteers, and 35% is a statistic
Asked what the central limit theorem says, a student replies, "As you take larger and larger
samples from a population, the histogram of the sample values looks more and more Normal."
Is the student right? Explain your answer. correct answers No. The central limit theorem says
nothing about the histogram of the sample values. It deals only with the distribution of the
sample means.
The sampling distribution of a statistic is: correct answers The distribution of values taken by a
statistic in all possible samples of the same size from the same population
A statistic is said to be unbaised if: correct answers the mean of its sampling distribution is equal
to the true value of the parameter being estimated
Scores on the Critical Reading part of the SAT exam in a recent year were roughly Normal with
mean 495 and standard deviation 118. You choose an SRS of 100 students and average their SAT
Critical Reading scores. If you do this many times, the mean of the average scores you get will
be close to correct answers 495.
Scores on the Critical Reading part of the SAT exam in a recent year were roughly Normal with
mean 495 and standard deviation 118. You choose an SRS of 100 students and average their SAT
