Unit 1
What does SOCS stand for?
Shape, Outliers, Center, and Spread
What does a response variable measure?
The outcome of a study
What is a benefit of using a random sample for an observational study?
The results of the observational study can be generalized to the population
A certain computer chip company has a machine that makes a large number of computer chips. Of the computer chips produced on this machine, 3% are defective. Miriam, the quality control inspector, will randomly select computer chips from the machine to inspect.
What is the probability that the first defective computer chip Miriam finds is the sixth computer chip she inspects from the machine?
(0.97)5 (0.03)
For which of the following conditions is it not appropriate to assume that the sampling distribution of the sample mean is approximately normal?
A random sample of 10 taken from a population distribution that is skewed to the right
What is the formula for the mean?
sum of data values / number of data values
Which graph shows the relationship between two quantitative variables measured for the same individuals?
A scatterplot
A well-designed experiment should have which of the following characteristics?
I. Subjects assigned randomly to treatments
II. A control group or at least two treatment groups
III. Replication
I, II, and III
Ninety percent of the people who have a particular disease will have a positive result on a given diagnostic test. Ninety percent of the people who do not have the disease will have a negative result on this test. If 5 percent of a certain population has the disease, what percent of that population would test positive for the disease?
14%
There were 5,317 previously owned homes sold in a western city in the year 2000. The distribution of the sales prices of these homes was strongly right-skewed, with a mean of $206,274 and a standard deviation of $37,881. If all possible simple random samples of size 100 are drawn from this population and the mean is computed for each of these samples, which of the following describes the sampling distribution of the sample mean?
Approximately normal with mean $206,274 and standard deviation $3,788
The average of the two middle values in the ordered list.
What does FUDS stand for?
Form, unusual features, direction, and strength
When is it preferable to use stratified random sampling rather than simple random sampling?
The population can be divided into strata so that the individuals in each stratum are as much alike as possible.
A police officer is using a radar device to check motorists’ speeds. Prior to beginning the speed check, the officer estimates that 40 percent of motorists will be driving more than 5 miles per hour over the speed limit. Assuming that the police officer’s estimate is correct, what is the probability that among 4 randomly selected motorists, the officer will find at least 1 motorist driving more than 5 miles per hour over the speed limit?
0.8704
A bag contains chips of which 27.5 percent are blue. A random sample of 5 chips will be selected one at a time and with replacement. What are the mean and standard deviation of the sampling distribution of the sample proportion of blue chips for samples of size 5?
The mean is 0.275, and the standard deviation is (Square root) 0.275(0.725) / 5
The mean age of 10 students in the classroom is 16 years old. A 7-year-old leaves the room. What is the mean age of the remaining 9 students in the classroom?
17 years old
What is r2 of a regression line that has a correlational coefficient of .89?
.7921
A florist wanted to investigate whether a new powder added to the water of cut flowers helps to keep the flowers fresh longer than just water alone. For a shipment of roses that was delivered to the store, the florist flipped a coin before placing each rose in its own individual container with water. If the coin landed heads up, the rose was placed in water with the new powder; otherwise, the rose was placed in water alone. What is the best description of the method used by the florist?
An experiment with a completely randomized design
A player pays $15 to play a game in which a chip is randomly selected from a bag of chips. The bag contains 10 red chips, 4 blue chips, and 6 yellow chips. The player wins $5 if a red chip is selected, $10 if a blue chip is selected, and $20 if a yellow chip is selected. Let the random variable X represent the amount won from the selection of the chip, and let the random variable W represent the total amount won, where W = X - 15. What is the mean of W?
-$4.50
Researchers are studying populations of two squirrels, the eastern gray and the western gray. For the eastern gray squirrel, about 22 percent of the population weighs over 0.5 kilogram (kg). For the western gray squirrel, about 36 percent of the population weighs over 0.5 kg. A random sample of 60 squirrels will be selected from the population of eastern gray squirrels, and a random sample of 120 squirrels will be selected from the population of western gray squirrels. What is the mean of the sampling distribution of the difference in sample proportions (eastern minus western) ?
0.22 - 0.36
The average yearly snowfall in Chillyville is approximately normally distributed with a standard deviation of 4.83 inches. If the snowfall in Chillyville exceeds 60 inches in 15% of the years, what is the mean?
55 inches
What is the equation for the least-squares regression line?
(y-hat) = a + bx
The director of a fitness center wants to examine the effects of two exercise classes (spinning and aerobics) on body fat percentage. A six-week spinning class and a six-week aerobics class are offered at the same time and on the same days, so that a person can enroll in only one of them. A new class of each is about to begin, and each class has 25 people in it. Ten people are randomly selected from each class. Each person's body fat percentage is measured at the beginning and again at the end of the six-week class. Using the change in body fat percentage as the response variable and conducting a test at the a = 0.01 level, the director determines that there is a significant difference between the treatment means. What is a confounding variable in the study?
The participants' choice of which class to take.
A box contains 10 tags, numbered 1 through 10, with a different number on each tag. A second box contains 8 tags, numbered 20 through 27, with a different number on each tag. One tag is drawn at random from each box. What is the expected value of the sum of the numbers on the two selected tags?
14.5
At a certain high school, the distribution of backpack weight is approximately normal with mean 19.7 pounds and standard deviation 3.1 pounds. A random sample of 5 backpacks will be selected, and the weight, in pounds, of each backpack will be recorded.
For samples of size 5, which of the following is the best interpretation of P(x > 22) = .05?
For all samples of size 5, the probability that the sample mean will be greater than 22 pounds is approximately 0.05.