stats midterm multiple choice

The protein content for the 15 bean varieties has a mean of 12.2 grams and a standard deviation of 5.3 grams. The mean carbohydrate content is 33.6 grams with a standard deviation of 15.7 grams. The correlation is 0.84. Which of the following expressions represents the slope of the least squares regression of y= protein content on x= carbohydrate content?

a. (0.84)(5.3)/(15.7)

A 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 & x. Which of the following is the best approximation of the correlation of x & y.

a. -0.84

Forty pound bags of bird seed do not have exactly 40 pounds of seed, but the weight of the 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 for the 90th percentile for the weight of these bags of seed?

a. 40.3 lbs

Mr. Lee has 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. Below is a histogram of the word counts for the 24 essays. Which of the following best describes the distribution the variable Number of Words in these essays?

a. Skewed right, centered at about 750, with one high outlier

Which of the following is the most important reason for randomly assigning subjects to treatment groups in an experiment?

a. To create groups that are as similar as possible

The unusual point in the upper left part of the plot is 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 the data set?

a. the correlation would be closer to 1, because the remaining data would have a stronger positive relationship.

One hundred people work at Lagtime Internet Services. Suppose after a particularly successful year, the president of the company decided to double his own salary and not change anyone else's. Assuming the president makes more than anyone else, which of the following statements about changes un measures of center and spread is true?

a. the mean and standard deviation will increase, but the median interquartile range will stay the same

Let E = {People in a random sample who regularly use the internet as a source of news.}Let P = {People in the same random sample who regularly use print media as a source of news.} The Venn diagram below summarizes the distribution of these two categorical variables.

b.

All of the following small data sets have a mean of 5. Which one has the lowest standard deviation?

b. 1 3 5 5 5 7 9

You randomly select one truck owner. What is the probability that he or she owns a Chevy, given that the truck has four-wheel drive?

b. 32/80

The heights (in centimeters) of the male and female students in a class are summarized in the following box plots Which of the following conclusions can be drawn from this graph?

b. About 25% of the male students are taller than the tallest female student

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 times Danica washes her car has a mean of 15 with standard deviation of 4. What are the mean and standard deviation of the net gain Danica receives if she buys a membership card?

b. Mean=5; Standard deviation= 8

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 higher. Which one of the following sets of measurements will he have to recalculate.

b. The mean and standard deviation

At right are box plots describing the distribution of prices paid for homes in two suburbs ofColumbus, Ohio over a single 30-day period in 2012. Which of the following statements issupported by the information in this graph?

b. The median house price in Dublin is higher than the 75th percentile of house pricein Westerville.

Which of the following is the best description of a simple random sample of size n from a population of size N?

b. any method of sampling in which every group of individuals of size n is equally likely to be selected

What is the principle purpose of control in a randomized comparative experiment?

b. isolating the effect of the treatment variable by keeping all other variables the same in the treatment groups

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?

b. stratified random sample

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= daily profit (in dollars).

c. $13

In 1965, the mean price of a new car was $2,650 and the standard deviation was $1000. In 2011, themean was $30,500 and the standard deviation was $9000. If a Ford Mustang cost $2300 in 1965and $28,000 in 2011, in which year was it more expensive relative to other cars?

c. 2011, because the standard score is higher than in 1965

The following is a histogram showing the actual frequency of the closing prices on the New York exchange of a particular stock over a 50 day period. The class that contains the 3rd quartile is

c. 30-40

Which of the following statements about standard deviation is true?

c. Standard deviation is always a non-negative number

When testing water for chemical impurities, results are often reported as bdl, that is, below detection limit. The following are the measurements of the amount of lead in a series of water samples taken from inner-city households Which of the following is correct?

c. The median lead level is 7ppm

The weights of adult male 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?

c. The proportion of adult male Labrador Retrievers that weigh less than 80 pounds is approximately equal to the proportion that weigh more 94 pounds.

A researcher reports that, on average, the participants in his study lost 10.4 pounds after two months on his new diet. A friend of yours comments that she tried the diet for two months and lost no weight, so clearly the report was a fraud. Which of the following statements is correct?

c. The report only gives the average. This does not imply that all participants in the study lost 10.4 pounds or even that all lost weight. Your friend's experience does not necessarily contradict the study results.

At right is a stem plot of the weights of 18 adult Maine Coon Cats. Which one of the following statements must be true about this distribution?

c. The standard score for a 14-pound cat is negative

You randomly select one truck owner. Which one of the followings true about the events "Owner has a Chevy" and "Owner's truck has four-wheel drive"?

c. These two events are not mutually exclusive, but they are independent.

Which of the following is NOT true about standard deviation?

c. if the units for the data are in inches, standard deviation is in square inches

The customer service department of an online store keeps track of the length of time customers wait on hold for a representative. The mean wait time is 5 minutes and the standard deviation is 2.3 minutes. Suppose the company wants to change the variable from minutes to seconds exceeding a target time of 120 seconds. That is, if X is wait time on minutes, the new variable is Y= 60X-120. Which of the following are the mean and standard deviation of Y?

c. mean= 180; Standard deviation = 138

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?

c. the probability of "success" is the same fro each trial

Which of the following best describes what S=20.7237 measures?

c. the standard deviation of the residuals

The least squares regression line minimizes which of the following quantities?

c. the sum of the squared differences between the observed values of the response variable and the predicted values of the response variable

For the track coach's study described in the previous exercise, which of the following best describes a conclusion that can be drawn?

c. we can determine whether the new training program improves race times more than the standard program for the distance runners in this study

A recent investigation of prices for five-year-old Toyota Camrys in Montgomery, Alabama, and New York, New York, revealed that the mean price in Montgomery was $13,200 with a standard deviation of $1000. In New York, the mean price was $12,800 with a standard deviation of $1800. Which of the following statements is true?

c.the standard score for a car priced at $15,000 would be higher in Montgomery than in New York.

A hat holds a large number of slips of paper, each with a single digit from 1 to 4 on it. Which one of the following is a possible probability distribution for the number on a single randomly-selected slip of paper?

d.

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?

d. .614

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?

d. 110- (101.24 + 0.02977 * 953)

The cumulative relative frequency graph at right shows the distribution of lifespans for 39 U.S.presidents. Which of the following is closest to the 70th percentile of this distribution?

d. 77 years

You randomly select one truck owner. What is the probability that he or she owns a Dodge or has four-wheel drive?

d. 90/125

The same 1200 tomatoes from question #9 have a mean weight of 143 grams and a standard deviation of 35 grams. If the weights are Normally distributed, approximately how many tomatoes weigh between 73 grams and 178 grams?

d. 978

If P(A) = 0.6; P(B) = 0.2, and P(A & B)= 0.1, which of the following must be true?

d. A and B are neither independent or mutually exclusive

If you flip three coins, the probability of getting three heads is o.125. Which of the following statements follows from this?

d. If you flip three coins 5000 times, the percentage of time you get three heads will be very close to 12.5%

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 a day with a standard deviation of 4.5 pounds. Which of the following are the mean and approximate standard deviation of the total weight of lobsters John traps in a day?

d. Mean=22; Standard deviation= 8.32

For the density curve shown at right, which letters correspond to the locations of the mean and median of the distribution?

d. Median=B; Mean=A

The bar graph at right shows the distribution of religious affiliation around the world. Which of the following statement best describes what is wrong with this graph?

d. Starting the vertical scale at 5 distorts the relative frequency of the religions

According to the U.S. Bureau of Labor Statistics, the monthly percentage change in the number of jobs in a certain state for the twelve months of 2011 had a mean of .08% and a standard deviation 1.7% From this information we can conclude that ...

d. The magnitude of the monthly deviations from the mean change averaged about 1.7%

A forester studying oak trees finds that the correlation between x= the age (measured in years) and y= height (in feet) of a sample of trees is 0.78. Which of the following statements must be true?

d. if we measure the height in meters instead of feet, the correlation would still be 0.78.

For the data in the previous problem, which measures of center and spread would be most appropriate to use?

d. median and interquartile range

Some studies of the relationship between car color and frequency of accidents have found that red cars are more likely to be in accidents 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 cofounding. Which of the following best describes what this means.

d. 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 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?

d. the mean will be greater than the media

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?

d. 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.

The graph below shows how mothers of young children respond to the question, "How many times a week do you choose fast food as a dining option for your family?" What's wrong with this method of presenting information?

d. using proportionally-sized hamburgers exaggerates differences between responses

Which of the following is closest to the 61st percentile of a standard normal distribution?

d. z=0.28

An inspector examines a large shipment of several thousand laser pointers by randomly selecting and then inspecting 6 laser pointers. Suppose that 1% of the laser points are defective. Which one of the following expressions describes the probability that exactly one of the six laser pointers is defective?

e. (0.99)^5 (0.01)

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(one is missing) Which of the following is the probability of rolling an odd number?

e. 0.6

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?

e. 0;1

The five-number summary of the weights (in grams) of 1200 tomatoes grown in a certain greenhouse was 90 113.5 140 161 236. How many tomatoes weighed less than 161 grams?

e. 900

The median age of five people in a meeting is 30 years. One of the people- a 50 year old- leaves the room. The median age of the remaining four people in the room is ...

e. can not be determined from the information given

A track coach wants to test the effectiveness of a new training program for distance runners. He selects his fastest two runners and, using a coin flip, randomly chooses one to participate in the new program. The other will continue with the standard training program. He then picks the next two fastest runners and randomly assigns one to each program. He repeats this process with all his group of two runners. What is the name of the kind of experimental design?

e. matched pairs design

At the beginning of the school year, a high school teacher asks every student in her classes to fill out a survey that asks for their age, gender, their number of years they have lived at their current address, their favorite school subject, and whether they plan to go to college after high school. Which of the following best describes the types of variables that are being measured?

e. three categorical variables and two quantitative variables