STA2023- Spring 2013 - Ripol EXAM 1 February 19, 2013

STA2023- Spring 2013 - Ripol EXAM 1 February 19, 2013

Instructions:

• This exam contains 33 Multiple Choice questions. Please select the best answer among the alternatives given.
• Each question is worth 3 points, for a total of 99 points. The last point will be awarded for correctly bubbling in your name, UFID number and Test Form Code on the scantron sheet and showing your GatorOne picture ID.
• YOU MUST SIGN, IN INK, the Honor Pledge on the next page of the exam and the back of the scantron sheet. The proctors will compare them to the signature on the ID.
• You may write whatever you want on this test, but only the answers bubbled in the scantron sheet will be graded.
• Make sure you mark all your answers on this test so you can compare your answers to the key that will be posted on the course website.
• This page contains Tables and Formulas, plus some blank space to be used as scratch paper.You may detach this page from the exam but make sure the rest of the exam does not fall apart!

Formulas:

res= obs y – pred y

P(A and B) = P(A) P(B) P( A | B) = P( A and B) / P(B)

STA2023- Spring 2013 - Ripol EXAM 1 TEST FORM A February 19, 2013

Honor pledge: "On my honor, I have neither given nor received unauthorized aid on this examination."

The following pie charts represent the distribution of Freshmen, Sophomores, Juniors and Seniors enrolled this semester in STA 2023 (all students) and attending the live lecture in Norman Hall the first week of classes.

1. These graphs are an example of which area of the field of Statistics?

a) Designb) Descriptionc) Inferenced) Probabilitye) Empirical

2. Which of the following statements is NOT true?

a) The first graph represents the entire population of students enrolled in the course this semester.

b) The second graph represents a random sample of the population enrolled in the course this semester.

c) The average year in school would be a lot lower for students who attend the live lecture than for the whole class.

d) Less than half of the sophomores enrolled in the class were present in the live lecture the first week.

e) Freshmen are much more likely to come to the live class during the first week than upperclassmen.

3. Which of the following could be the distribution of students in the whole class according to the graph?

a) Freshmen 20% Sophomores 57 % Juniors 26% Seniors 6%

b) Freshmen 20% Sophomores 52 % Juniors 23% Seniors 5%

c) Freshmen 18% Sophomores 52 % Juniors 23% Seniors 5%

d) Freshmen 74% Sophomores 18 % Juniors 3% Seniors 1%

e) Freshmen 74% Sophomores 21 % Juniors 4% Seniors 1%

4. The correlation of a data set can never be:

a) zerob) negativec) greater than 0.5d) greater than 100e) smaller than 0.5

5. The amount of soda a dispensing machine pours into a 12 ounce can of soda follows a normal distribution with a mean of 12.54 ounces and a standard deviation of 0.36 ounce. The cans only hold 12.9 ounces of soda. Every can that has more than 12.90 ounces of soda poured into it causes a spill. What proportion of cans end up spilling?

a) 0.1587

b) 0.3413

c) 0.8413

d) 0.6587

e) 0.7933

The following information appears on many webpages for high schools in Florida that offer the Cambridge program (AICE): “AICE students are better prepared to be successful at the University level upon graduation from high school. A study recently done by Bill Kolb, director of admissions at the University of Florida, showed that AICE students performed better during their freshman year at UF than students who took IB, AP and Dual Enrollment courses.” Acceleration Mechanism Average GPA Freshman Year

None (honors or regular classes) 2.60

Dual Enrollment 2.65

Advanced Placement (AP) 3.02

International Baccalaureate (IB) 3.08

Advanced International Certificate in Education (AICE) 3.46

Identify the following:

6. Factor(s) ____a) Acceleration Mechanism

7. Treatment(s) ____b) students

8. Experimental Unit(s) ____c) self-selection, courses taken during freshmen year, etc

9. Response Variable(s) ____d) AP, IB, AICE, Dual Enrollment, None

e) GPA

10. The best way of graphically representing this data set would be to use:

a) a scatterplotb) a contingency table

c) pie chartsd) histogramse) side-by-side boxplots

11. Which of the following is one of the issues discussed during lecture that dispute the validity of the study?

a)The study was not conducted by UF, but by the directors of the Cambridge high schools.

b)The study was conducted by a group of UF students, not the director of admissions.

c)The sample size for one of the groups was less than five students.

d)The study was done on Freshmen who enrolled at UF in the year 1995.

e)The study was intentionally biased against students who did not participate in AICE.

12. This is an example of:

a)How introducing a third variable can lead to different conclusions - Simpson’s paradox.

b)How the Empirical Rule applies to all data sets that meet the right conditions.

c)How extrapolation beyond the observed data can lead to misleading conclusions.

d)How influential outliers can skew the results of a study dramatically.

e)How association between two variables does not automatically imply causation.

The probability distribution of the number of siblings students have is shown below.

13. What is the shape of the probability histogram for this distribution?

14. Find the mean of the probability distribution shown above.

a) 1b) 2.5 c) 1.68d) 2 e) 1.79

15. A sample of 10 students in the class was asked to report the number of siblings they had.

Find the standard deviation for this sample. 4 0 2 0 0 2 1 1 2 3

a) 1.35b) 1.28c) 1.32d) 1.25e) 1.07

16. The mean and standard deviation computed in the previous two problems are:

a) both parametersb) a statistic and a parameter, respectively

c) both statisticsd) a parameter and a statistic, respectivelye) both unbiased

17. The standard deviation of a data set can never be:

a) zerob) negativec) greater than 0.5d) greater than 100e) smaller than 0.5

A study asked students to report how many hours they exercised on a typical week while they were in high school, and now while in college. The regression analysis to predict college exercise appears on the graph.

18. Which of the following is the best interpretation ofthe slope?

a) For each extra hour a week of exercise a student did in high school we can predict his college exercise increases by 2.22 hours per week.

b) For each extra hour a week of exercise a student did in high school we can predict his college exercise increases by 0.4198 hours per week.

c) For each extra hour a week of exercise a student does in college we can predict his high school exercise used to be 2.22 hours per week higher.

d) For each extra hour a week of exercise a student does in college we can predict his high school exercise used to be 0.4198 hours per week higher.

e) The line predicts a smaller amount of exercise in college than high school for all students.

19. Which of the following is the best interpretation ofthe intercept?

a) Students who do not exercise in college used to exercise 2.22 hours a week in high school, on average

b) Students who do not exercise in college used to exercise 0.4198 hours a week in high school, on average

c) Students who did not exercise in high school now exercise 2.22 hours in college, on average

d) Students who did not exercise in high school now exercise 0.4198 hours in college, on average.

e) Students who did not exercise much in high school exercise a bit more in college, on average.

20. Interpret R2 = 28.3%.

a) 28.3% of the points in the data set fall on the regression line.

b) 28.3% of the points in the data set fall within one standard deviation of the regression line.

c) 28.3% of the variance in high school and college exercise hours has been explained by the regression line.

d) 28.3% of the variability in college exercise hours has been explained by the regression line.

e) 28.3% of students in the data set had variability in the number of hours they exercised in high school and college.

21. Is the point at (27, 60) an influential point?

a) Yes, because deleting it would change the slope from positive to negative.

b) Yes, because deleting it would make the correlation weaker.

c) No, because deleting it would make the correlation stronger.

d) No, because deleting it would not change the slope of the line very much.

e) No, because no one can exercise 60 hours a week.

22. A student who exercised 10 hours a week in high school reports 15 hours in college.

Find the residual.

a) 5.0 b) 1.5 c) 6.5d) 8.6 e) 3.6

The table presents parts of the results of a student survey. Find the probability that:

25. a student selected at random is a conservative that believes abortion should be legal?

a) 83/102 b) 83/135 c) 52/187 d) 52/135 e) 52/289

An achievement test has scores that are normally distributed with a mean of 1200 and a standard deviation of 150.

26. What score will put a student in the top 2%?

a) 950

b) 1350.25

c) 1507.5

d) 892.5

e) 1176

27. If 3,500 people took the achievement test, how many people scored lower than the 98th percentile?

a) 70

b) 3430

c) 3420

d) .02

e) .98

28. Bob has a z-score of -1.74 on the achievement test. What was his score?

a) 3288

b) 939

c) 261

d) 1461

e) 2088

29. Between what two values will you find the central 68% of all achievement test scores?

a) 1100 and 1300b) 1000 and 1400c) 900 and 1500

d) 1050 and 1350 e) 750 and 1650

The US Department of Transportation reports that, although 85% of all drivers routinely use a seat belt, for drivers of pick-up trucks the probability is only 75%. We will randomly sample 14 pick-up truck drivers and ask them if they routinely use a seat belt. Let X= number who answer yes in the sample.

30. Find the mean and standard deviation of X.

a) 11.9, 1.34b) 10.5, 1.62

c) 10.9, 1.25d) 11.5, 1.72

e) 11.2, 1.53

31. Find the probability that exactly 10 pick-up truck drivers report using a seat belt routinely.

a) 0.0563

b) 0.1769

c) 0.0030

d) 0.2202

e) zero

32. Which of the following formulas represents the probability that all of the pick-up truck drivers say yes?

a) (.25)14b) (.75)14

c) 1 - (.25)14d) 1 - (.75)14

e) 1 - (.25)(.75)

33. Which of the following formulas represents the probability that at least one pick-up truck driver says yes?

a) (.25)14b) (.75)14

c) 1 - (.25)14d) 1 - (.75)14

e) 1 - (.25)(.75)