MIDTERM EXAM REVIEW FOR STATS AND PROBABILITY 2013 Name ______
1. A random sample of n = 1000 portfolio rate returns (measured as a percentage) is taken; here are the data:
The distribution of the rate of returns is best described as:
a. skewed left
b. skewed right
c. symmetric
d. uniform
2. In the scatterplot below, the correlation is closest to:
- -0.87
- 0.25
- 0.99
- 1.03
3. An observational study was conducted to study the effects of pool accuracy (as measured by the percentage of made shots) and the number of (alcoholic) beers consumed for 25 pool players. For each player, it was recorded x = the number of beers consumed, and y = the percentage of made shots. For these 25 data pairs, the correlation was computed to be r = 0:07. What does this correlation tell about the relationship between alcohol intake and pool accuracy?
a. There is almost no relationship between alcohol and pool accuracy.
b. An increase in alcohol intake causes players to play worse.
c. Players will play their best before they have consumed any alcohol.
d. None of the above.
4. You are working at General Electric and are participating in a study that is examining the starting time of jet engines (y, measured in seconds) and the amount of thrust exerted by them (x, measured in a scale similar to horsepower"). In a recent study, 10 engines were tested and computed the least-squares regression line to be: TIME = 3:80 – 0:002 (THRUST)
What is the slope of the regression line for these data?
a. 3.80
b. -0:002
c. 0:002
d. It is impossible to tell without more information
5.If the life of wild pheasants follows a normal distribution with a mean of 9 months and a standard deviation of 3, what percent of the population will be less than 11 months of age? (Choose the closest.)
a. 34
b. 63
c. 75
d. 84
6. One hundred students took a test on which the mean score was 73 with a standard
deviation of 8. A grade of A was given to all who scored 85 or better. Approximately how many A's were there, assuming scores were normally distributed? (Choose the closest.)
a. 42
b. 7
c. 58
d. 5
e. 2
7. The data below are the final exam scores of 10 randomly selected history students and the number
of hours they slept the night before the exam. Find the equation of the regression line for the given data, reporting coefficients to the nearest hundredth. What would be the predicted score for a history student who slept 7 hours the previous night? Round your answer to the nearest whole number. Is this a reasonable question?
A) y = 5.04x + 56.11; 91; Yes, it is reasonable.
B) y= 5.04x + 56.11; 91; No, it is not reasonable. 7 hours is well outside the scope of model.
C) y= -5.04x + 56.11; 21; No, it is not reasonable. 7 hours is well outside the scope of model.
D) y= -5.04x + 56.11; 21; Yes, it is reasonable.
8. A student takes a standardized exam. The grader reports the student’s standardized score (z-score) as –1.8. This indicates:
a. The student scored lower than the average.
b. The student scored less than one standard deviation from the average.
c. A mistake has been made in calculating the score, since a standard score can never be negative.
d. Both a and b, but not c.
9. A correlation of r=0.85 indicates that the graph of the data would show
a. Points tightly packed around a line that slopes up to the right.
b. Points tightly packed around a line that slopes down to the right.
c. Points widely scattered around a line that slopes up to the right.
d. Points widely scattered around a line that slopes down to the left.
10. We conduct a regression and find that the least squares line is y=3+5x. This indicates that as the value
of x increases by 1 the expected value of y would increase by:
a. 5.
b. 8.
c. 23.
d. 20.
A study was conducted on the amount of time drivers wait for a stoplight to change at a particular intersection. The amount of time spent by 300 drivers was recorded and the resulting data were used to create this boxplot. Answer questions 11 through 13 for this data.
11. The median amount of time spent at this traffic light was
a. 1.0.
b. 2.3.
c. 4.0.
d. It is impossible to tell without the standard deviation.
12. The top 25% of drivers waited over
a. 1.3.
b. 2.3.
c. 4.0.
d. It is impossible to tell without the standard deviation.
13. The mean amount of time spent at this traffic light was
a. greater than the median.
b. less than the median.
c. about the same as the median.
d. It is impossible to tell without the standard deviation.
The midterm exam grades of a history course were used to create the following stem and leaf plot.
14. What is the first quartile of these scores?
a. 52
b. 73
c. 86
d. 93
15. Past data has shown that the regression line relating the final exam score and the midterm exam
score for students who take statistics from a certain professor is:
final exam = 50 + 0.5 × midterm
One interpretation of the slope is
a. a student who scored 0 on the midterm would be predicted to score 50 on the final exam.
b. a student who scored 0 on the final exam would be predicted to score 50 on the midterm exam.
c. a student who scored 10 points higher than another student on the midterm would be
predicted to score 5 points higher than the other student on the final exam.
d. students only receive half as much credit (.5) for a correct answer on the final exam
compared to a correct answer on the midterm exam.
16. For the stem-and-leaf plot below, what are the maximum, minimum , and median entries?
A) max: 47; min: 10; median 8
B) max: 47; min: 10; median 27
C) max: 47; min: 10; median: 28
D) max: 41; min: 10; median 28
17. Construct a frequency histogram:
18. Find the z-score for the value 60, when the mean is 86 and the standard deviation is 8.
A) z = -0.60 B) z = 0.60 C) z = -3.37 D) z = -3.25
19. The difference between the observed and predicted value of the response variable is a .
A) residual B) variance C) standard deviation D) z- score
20. IQ test scores are normally distributed with a mean of 99 and a standard deviation of 11. An
individual's IQ score is found to be 128. Find the z-score corresponding to this value.
A) 2.64 B) -2.64 C) 0.38 D) -0.38
21. Given the size of a human's brain, x, and their score on an IQ test, y, would you expect a positive
correlation, a negative correlation, or no correlation?
A) positive correlation B) negative correlation C) no correlation