stats mid term

Association is due to the presence of a lurking variable

A researcher observes that, on average, the number of divorces in cities with major league baseball teams is larger than cities without major league baseball teams. The most plausible explanation for this observed association is that the?

Slope would decrease; y intercept would increase

A dataset included the number of people per television set in the number of people per physician for 40 countries. The Fathom screen below displays a scatter plot of the data with the least squares regression line added. In Ethiopia, there were 503 people per TV and 36,600 people per doctor. What effect would removing this point have on the regression line?

.25

A fire department in a rural county reports that their response time to fires is approximately normally distributed with a mean of 22 minutes and a standard deviation of 11.9 minutes. Approximately what proportion of their response times is over 30 minutes?

Cluster sample

A maple sugar manufacturer wants to estimate the average trunk diameter of sugar maple trees in a large forest. There are too many trees to list them all and take a SRS, so he divides the forest into several hundred 10 m x 10 m plots, selects 25 plots at random, and measures the diameter of every single sugar maple in each one. This is an example of a?

Control the effects of outside variables on the outcome

Control groups are used in experiments in order to?

The number of books a person finished reading last month

Data will be collected on the following variables. Which variable can be considered discrete?

The mean and median are equal

For the density curve shown in Question 1, which statement is true?

The density curve is symmetric

For the density curve shown, which statement is true?

16%

For the distribution of cookie bags described in question three, approximately what percent of the bags will likely be underweight (that is, less than 16 ounces)?

Grade 12 had the least relative frequency of participating students

In a certain school district, students from grade 6 through grade 12 can participate in a school sponsored community service activity. The following bar chart shows the relative frequencies of students from each grade who participate in the community service activity. Which of the following statements is supported by the bar chart?

Skewed right

Mean greater than the median.

Skewed left

Mean less than the median.

The interquartile range

One statistic calculated for pictures in baseball is called the earned run average, or ERA. The following box plot summarize the ERA for pictures in two leagues, A and B. Based on the box plots, which of the following statistics is the same for both leagues?

34%

Suppose that 16 ounce bags of chocolate chip cookies are produced with weights that follow a normal distribution with a mean way 16.1 ounces and standard deviation .1 ounce. The percent of bags that will contain between 16.0 and 16.1 ounces is about?

The observation in the lower-right corner of the plot is influential for the least-squares line

The British government conducts regular surveys of household spending. The average weekly household spending on tobacco products and alcoholic beverages for each of the 11 regions in Great Britain was recorded. A scatterplot of spending on alcohol versus spending on tobacco is shown below. Which of the following statements is true?

.5631

The area under the standard normal curve corresponding to -.03 < z < 1.6 is?

1.2 centimeters

The cumulative relative frequency graph at right shows the distribution of lengths of fingerlings at a fish hatchery. The interquartile range for this distribution is approximately?

Skewed to the right, with mean 0 and standard deviation 1

The distribution of the time it takes for different people to solve a certain crossword puzzle is strongly skewed to the right, with a mean of 30 minutes and a standard deviation of 15 minutes. The distribution of the z scores for those times is?

The square of the correlation coefficient

The percent of the variation in the values of y that is explained by the least squares regression of y on X is?

16.5 degrees Fahrenheit

There is a linear relationship between the number of chirps made by the striped ground cricket and the air temperature. A least square fit of some data collected by a biologist gives the model Y= 25.2+3.3 X, where ask is the number of chirps per minute and Y is the estimated temperature in degrees Fahrenheit. What is the predicted increase in temperature for an increase of five chirps per minute?

A matched pairs experiment

To test the effect of music and productivity, a group of assembly line workers are given portable MP3 players to play whatever music they choose while working for one month. For another month, they work without music. The order of the two treatments for each worker is determined randomly. This is?

86

What was the activity level rating for the fish at a temperature of 20.4 degrees Celsius?

The correlation will also be -.44

When we standardize the values of a variable, the distribution of standardized values has a mean of zero and a standard deviation of one. Suppose we measure two variables, X and Y, on each of several subjects. We standardize both variables and then compute the least squares regression line. Suppose to slope of the least square regression line is -.44. We may conclude that?

The average distance of the activity level ratings from the least-squares line is about 4.785

Which of the following gives a correct interpretation of s in this setting?

They are symmetric AND the curve reaches its peak at the mean

Which of the following properties is true for all normal density curves?

R is measured in inches

Which of these is NOT true of the correlation r between the lengths in inches and weights in pounds of a sample of brook trout?

If the person owns a car, he or she is more likely to live elsewhere in the city than to live in the downtown area in the city

A local company is interested in supporting environmentally friendly initiatives such as carpooling among employees. The company surveys all of the 200 employees at the downtown offices. Employees responded as to whether or not they own a car and to the location of the home where they live. The results are shown in the table below. Which of the following statements about a randomly chosen person from these 200 employees is true?

75%

A medical researcher collects health data on many women in each of several countries. One of the variables measured for each woman in the study is her weight in pounds. The following list gives the five number summary for the weights of adult women in one of the countries. About what percent of Country A women weigh between 110 and 240 pounds?

Nothing, because there is no control group for comparison

A new headache remedy was given to a group of 25 subjects who had headaches. Four hours after taking a new remedy, 20 of the students reported that their headaches had disappeared. From this information you can conclude?

A specific storage time, a fruit pack, amount of vitamin C

A nutritionist wants to study the effect of storage time on the amount of vitamin C present in freeze dried fruit when stored for these lengths of time. Vitamin C is measured in milligrams per 100 mg of fruit. Six fruit packs were randomly assigned to each of the three storage times. The treatment, experimental unit, and responses are respectively?

Randomization is a good way to create two groups of 30 families that are as similar as possible, so that comparisons can be made between the two groups.

A researcher for consumer products company is field testing a new formula for laundry detergent. He has contracted with 60 families, each with two children, who have agreed to test the product. He randomly assigns 30 families to the group that will use the new formula and 30 to the group that we use the company's current detergent formula. The most important reason for this random assignment is that?

There is no linear relationship between number of activities and grade point average for students at this school

A school guidance counselor examines the number of extracurricular activities that students do and their grade point average. The guidance counselor says, the evidence indicates that the correlation between the number of extracurricular activities a student participates in and his or her grade point average is close to zero. A correct interpretation of the statement would be that?

Whether there is an association between sex and starting salary among graduates of this nursing school

A survey is to be administered to recent graduates of a certain nursing school in order to compare the starting salary of women and men. For a random sample of graduates, three variables are to be recorded: sex, starting salary, and area of specialization. Which of the following best describes the conclusion that can be drawn from the study?

The results will be the same regardless of the time of day that the sample is taken

A survey was done in the town of Mechanicsville to estimate the proportion of cars that are red and made by companies based in Japan. A random sample of 25 cars from the student parking lot at Lee Davis high school was taken. Which of the following statements is not correct?

If the student had used a calculator as the explanatory variable, the correlation would remain the same

An AP statistics student designs an experiment to see whether today's high school students are becoming too calculator dependent. She prepares two quizzes, both of which contain 40 questions that are best done using paper and pencil methods. A random sample of 30 students participate in the experiment. Each student takes both quizzes, one with a calculator and one without, in a random order. To analyze the data, the student constructs a scatter plot of the displays the number of correct answers with and without a calculator for each of the 30 students. Which of the following statements is true?

One-half of the students chose vanilla or chocolate

The following frequency table shows the responses from a group of college students who were asked to choose their favorite flavor of ice cream. Which of the following statements is NOT supported by the table.

More delays were caused by the weather than by all other reasons combined

The following pie chart summarizes the results of a survey given to airlines about the primary reason for flight delays. Which of the following statements is supported by the pie chart?

The distribution is skewed right

The graph at right is a normal probability plot for the amount of rainfall obtained from 26 randomly selected clouds that were seeded with silver oxide. Which of the following statements about the shape of the rainfall distribution is true?

It could be any number between 64 and 68 miles per hour

The main speed of vehicles in the cars only lanes of the New Jersey Turnpike is 68 mph. The main speed of vehicles in the any vehicle lanes is 64 mph. What must be true about the main speed of all vehicles on the turnpike, assuming these are the only types of lanes?

The distance between the weight of each infant born in April and the mean weight was, on average, about 10.2

The mean birth weight of infants born at a certain hospital in the month of April was 128 ounces with a standard deviation of 10.2 ounces. Which of the following is a correct interpretation of standard deviation?