Stats Midterm
Jocelyn runs a small mail-order bumper-sticker business. Based on daily sales figures for the past two years, she has developed the following probability distribution for X= fail profit (in dollars). Which of the following is the expected value of X.
$13
An inspector examines a large shipment of laser pointers by randomly selecting a pointer, one at a time, until he finds one that is defective. Suppose that 1% of the laser points are defective. Which one of the following expressions describes the probability that the first defective pointer he finds is the sixth one that he selects?
(0.99)^5(0.01)
The protein content for the 15 bean variety has a mean of 12.2 grams and a standard deviation of 5.3 grams. The mean carbohydrate content is 33.6.... Which of the following represents the slope of the least squares regression of y=protein content on x=carbohydrate content?
(o.84)(5.3)/(15.7)
An efficiency consultant determines that on the assembly line at Widget Manufacturing, there is a strong, negative, linear relationship between x= the number of consecutive hours a worker has been assembling widgets and y= the number of widgets he can produce in an hour. He finds that 70% of the variation in widgets produced per hour can be explained by the regression of y on x. Which of the following is the best approximation of the correlation of x and y?
-0.84
A special 20-sided die is constructed so that each face has either a 1,2,3 or 4 on it. The table below gives the probability of each value. Which of the following is the probability of rolling an odd number?
0.6
Gabriel has determined that if he gets to the bus stop by 7:30 am, there is a 0.15 probability that he misses the bus. If he is at the bus stop three consecutive days at 7:30, what is the approximate probability that he CATCHES the bus all three days?
0.614
All of the following small data sets have a mean mof 5. Which has the lowest standard deviation?
1 3 5 5 5 7 9
One flight-Philadelphia to West Palm Beach, FL-is 953 miles long and costs $110. Which of the . following expressions correctly represents the . residual for this data point?
110-(101.24+0.02977x953)
In 1965, the mean price of a new car was $2,650 and the standard deviation was $1000. In 2011 the mean was $30,500 and the standard deviation was $9000. If a Ford Mustang cost $2300 in 1965 and $28,000 in 2011, in which year was it more expensive relative to other cars?
2011, because the standard score is higher than in 1965
The following is a histogram of the New York Stock Exchange... The class that contains the 3rd quartile us...
30-40
You randomly select one truck owner. What is the probability that he owns a Chevy, given that he has four wheel drive?
32/80
Forty pound bags of bird seed do not have exactly 40 pounds of seed, but the weight of seeds is approximately Normally distributed with a mean of 40 pounds and a standard deviation of 0.25 pounds. Which of the following is the best estimate of the 90th percentile for the weight of these bags of seed?
40.3 pound
The cumulative relative frequency graph at right shows the distribution for 39 US presidents. Which of the following is closest to the 70th percentile of this distribution?
77 years
You randomly select one truck owner. What is the probability that he owns a Dodge OR has four wheel drive?
90/125
The five-number summary for the weights of 1200 tomatoes grown in a certain greenhouse was 90 113.5 140 161 236. How many tomatoes weighed less than 161?
900
If P(A)=0.6; P(B)=0.2; and P(AnB)=0.10, which of the following must be true?
A and B are neither independent nor mutually exclusive
The heights of the male and female students in a class are summarized in the following..... Which of the following conclusions can be drawn from this graph?
About 25 percent of the male student are taller than the tallest female students
Which of the following is the best description of a simple random sample of size n from a population size of N?
Any method of sampling in which every group of individuals of size n is equally likely to be selected.
Which of the following is NOT true about standard deviation?
If the units for the data are in inches, standard deviation is in square inches
If you flip three coins, the probability of getting three heads is 0.125. Which of the following statements follows from this?
If you flip three coins 5000 times, the percentage of time you get three heads will be very close to 12.5%
What is the principle purpose of control in a randomized comparative experiment?
Isolating the effect of the treatment variable by keeping all other variables the same in the treatment groups
A track coach wants to test the effectiveness of a new training program for distance runners. He selects his two fastest runners and, using a coin flip, randomly chooses one to participate in the new program. The other will continue with the standard training regimen. He then picks the next two fastest runner and randomly assigns one to each program. He repeats this process with all his runners, choosing the two fastest remaining each time. He then compares race times within each group of two runners. What is the name for this kind of experimental design?
Matches pairs design
For the data in the previous problem, which measures of center and spread would be most appropriate to use?
Median and interquartile range
For the density curve shown at right, which letters correspond to the locations of the mean and median of the distribution?
Median=B; Mean=A
Mr. Lee as just collected his last batch of 24 English essays, all of them as computer files. He's curious about how long the papers are, but he doesn't want to be fooled by large font sizes, so he uses the word processing software's word count feature. Which of the following best describes the distribution the variable Number of Words in these essays?
Skewed right, centered at about 750, with one high outlier.
Which of the following ststements about standard deviation is true?
Standard deviation is always a non-negative number
The bar graph at right shows the distribution of religious affiliation around the world. Which of the following statements best describes what is wrong with the graph?
Starting the vertical scale at 5 distorts the relative frequency of the religions.
An airline has 10 daily flights from Philadelphia to Denver. To assess customer satisfaction, a random sample of 15 passengers from each flight on a single day are asked to fill out a survey about their experience on the flight. What type of sample is this?
Stratified random sample
Some studies of the relationship between car color and frequency of accidents have found that red cars are more likely to be in accident than black cars, despite how visible they are. Some experts warn that we should not conclude that red cars are less safe than black cars, because of possible confounding. Which of the following best describes what this means?
Studies of this type are all observational, and it is not possible to separate the effect of car color from the type of people who choose to drive red cars.
The unusual point in the upper left part of the plot for navy beans, with 15.8 grams of protein and 15.8 grams of carbohydrates. Which of the following best describes how correlation would change if we removed navy beans from this data set?
The correlation would be closer to 1, because the remaining data would have a stronger positive relationship.
According to the US Bureau, the mean is 0.08 and standard deviation is 1.70
The magnitudes of the monthly deviations from the mean change averaged about 1.70
A biology teacher has just finished grading a quiz for a class of 26 students and has calculated measures of center and spread on the scores. While writing the grades on the quizzes, he realizes he made a mistake, and the highest grade should be 10 points of higher. Which one of the following sets of measurements will he have to recalculate?
The mean and standard deviation
One hundred people work at Lagtime Internet Services.....Which of the following statements about changes in measures of center and spread is true?
The mean and standard deviation will increase, but the median and interquartile range will stay the same.
The time it takes people to finish a certain kind of puzzle is strongly skewed right. Which of the following statements is true about the mean and median of this distribution?
The mean will be greater than the median
At right are box plots describing the distribution of prices paid for homes in two suburbs of Columbus, Ohio over a single 30-day period in 2012. Which of the following statements is supported by the information in this graph?
The median house price in Dublin is higher than the 75th percentile of house price in . Westerville.
When testing water for chemical impurities... which of the following statements can we be sure is true?
The median lead level in the water is about 7ppm
A voting rights group randomly selects one individual voter from each of 20 different voting districts in a small city and asks him or her if they voted in the last national election. Let X= the number of people in the sample of 20 who voted. Which, if any, of the following requirements for X to be a binomial random variable is VIOLATED in this setting?
The probability of "success" is the same for each trial.
The weights of adult Labrador Retrievers are approximately Normally distributed with a mean of 87 pounds and a standard deviation of 8 pounds. Which of the following statements is true?
The proportion of adult male Labrador Retrievers that weigh less than 80 pounds is approximately equal to the proportion that weigh more than 94 pounds
A researcher reports that the participants lost mean of 10.4, friend reports loosing no weight... Which of the following statements is correct
The report gives only the mean. This does not imply that all participants in the study lost 10.4
Which of the following best describes what S=20.7237 measures?
The standard deviation of the residuals
At right is a templet of the weights of 18 adult Maine Coon Cats. Which one of the following statements must be true about his distribution?
The standard score for a 14 pound cat is negative.
A recent investigation of prices for five year old Toyota Camrys in Montgomery Alabama.... Which of the following statements is true?
The standard score for a car prices at $15,000 would be higher in Montgomery than in New York
The least squares regression line minimizes which of the following quantities?
The sum of the squared differences between the observed values of the . response variable and the predicted values of the response variable
A political action committee sends out a questionnaire to randomly-selected mailing addresses, asking people to rate the importance of a variety of economic and social issues facing the country. At the end of the questionnaire is an (optional) invitation to donate money to the organization. Which of the following statements about this survey is true?
The survey results will overestimate support for this political action committee in the entire population because people more likely to respond if they are prepared to donate money.
You randomly select one truck owner. Which one of the following is true about the events "Owner has a Chevy" and "Owner's truck has four wheel drive"?
These two events are not mutually exclusive, but they are independent.
Which of the following is the most important reason for randomly assigning subjects to treatment groups in an experiment?
To create groups that are as similar as possible
What's wrong with this method of presenting information?
Using proportionally sized hamburgers exaggerates differences between responses
For the track coach's study described in the previous exercise, which of the following best describes a conclusion that can be drawn?
We can determine whether the new training program improves race times more than the standard program for the distance runners in this study.
The median age of five people in a meeting is 30 years... The median age if the four remaining people in the room is=...
cannot be determined from the information given
The mean weight of pomegranates grown in a certain orchard is 16.5 ounces, with a standard deviation of 3.2 ounces. Which of the following best describes the mean and standard deviation of the standard scores of these pomegranates?
mean= 0 standard deviation= 1
John maintains two separate lines of lobster traps in Penobscot Bay. The East Bay traps produce a mean of 12 pounds of lobsters per day with a standard deviation of 7 pounds. The West Bay traps produce a mean of 10 pounds of lobsters per day with a standard deviation of 4.5 pounds. Which of the following are the mean and standard deviation of the total weight of lobsters John traps in a day?
mean= 22 standard deviation= 8.32
Capital Car Wash sells a membership card for $25 per year that entitles the buyer to a $2 discount on each car wash purchased during the year. The number of time Danica washes her car has a mean of 15 with a standard deviation of 4. What are the mean and standard deviation of the net gain Danica receives if she buys a membership card?
mean= 5 standard deviation= 8
At the beginning of the school year, a high-school teacher fills out survey, which of the following best describes the variables
three categorical variable and two quantitative variables
The customer service department . of an online store keeps track of the length of time . customers wait on hold for a representative..... .Which of the following are the mean and standard deviation of Y?
u=180; O=138
Which of the following is closest to the 61st percentile of a standard Normal distribution?
z=0.28
