Ap Stats Midterm Multiple-Choice

The five-number summary of the distribution of scores on the final exam is Psych 001 last semester was:

18 39 62 76 100.

Which of the following best describes the location of the 80th percentile?

A. 76

B. between 18and 39

C. Between 62 and 76

D. Between 76 and 100

E Probably between 39 and 76, since most of the class scored between these two numbers

D. Between 76 and 100

A score's percentile is the measure of...

A. Center

B. Spread

C. Relative Location

D. Skew

E. Relative Frequency

C. Relative Location

Here is a list of exam scores for the 14 students in Mr. Williams's calculus class:

60 61 61 65 72 75 75 78 81 85 89 91 98

What is the percentile of the person whose score was 85?

A. 15%

B. 21%

C. 29%

D. 71%

E. 85%

D. 71%

A standard score describes...

A. How much skew there is in a distribution

B. How much spread there is in a distribution

C. How far apart the mean and median of a distribution are

D. How far a particular score is from the mean

E. How far a particular score is from the median

D. How far a particular score is from the mean.

A soft-drink machine can be regulated so that it discharges an average of m oz. per cup. If the ounces of fill are Normally distributed with a standard deviation of 0.4 oz., what value should m be set at so that 98% of 6-oz. cups will not overflow?

A. 5.18

B. 6.00

C. 6.18

D. 6.60

E. 6.82

A. 5.18

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

I. They are symmetric

II. The curve reaches its peak at the mean

III. 95% of the area under the curve is within one standard deviation of the mean.

A. I only

B. II only

C. I and II only

D. I an III only

E. All three statements are correct

C. I and II only

The mean age (at inauguration) of all US Presidents is approx. Normally distributed with a mean of 54.6. Barak Obama was 47 when he was inaugurated, which is the 11th percentile of the distribution. Which of the following is closet to the standard deviation of president's ages?

A. -9.20

B. -6.18

C. 6.18

D. 7.60

E. 9.20

C. 6.18 using the z-score formula

A researcher wishes to determine whether the rate of water flow (in liters per second) over an experimental soil bed can be used to predict the amount of soil washed away (in kilograms). In this study, the explanatory variable is

A. Amount of eroded soil

B. Rate of water flow

C. Size of soil bed

D. Depth of soil bed

E. Liters/second

B. Rate of water flow

The correlation coefficient measures....

A. Whether there is a relationship between two variables

B. The strength of the relationship between two quantitative variables

C. Whether or not a scatterplot shows an interesting pattern

D. Whether a cause and effect relation exists between two variables

E. The strength of the linear relationship between two quantitative variables

E. The strength of the linear relationship between two quantitative variables

"Least-squares" in the term "least-squares regression line" refers to

A. Minimizing the sum of all the squares of all the values of explanatory variable

B. Minimizing the sum of the squares of all the values of the response variable

C. Minimizing the products of each value of the response variable and the predicted value based on the regression equations.

D. Minimizing the sum of the squares of the residuals

E. Minimizing the squares of the differences between each value of the response variable and each value of the explanatory variable.

D. Minimizing the sum of the squares of the residuals

Suppose we fit the least-squares regression line to a set of data. If a plot of the residuals shows a curved pattern,

A. A straight line is not a good summary for the data

B. The correlation must be 0.

C. The correlation must be positive

D. Outliers must be present

E. r^2= 0

A. A straight line is not a good summary for the data

If removing an observation from the data set would have a marked change on the equation of the least-squares regression line, the point is called

A. Resistant

B. A residual

C. Influential

D. A reponse

E. An outlier

C. Influential

Suppose a straight line is fit to data having response variable y and explanatory variable x. Predict values of y for values of x outside the range of the observed data is called

A. Contingency

B. Extrapolation

C. Causation

D. Correlation

E. Interpolation

B. Extrapolation

I toss a penny and observe whether it lands heads up or tails up, Suppose the penny is fair, i.e., the probability of heads is 1/2 and the probability of tales is 1/2. This means that

A. Every occurrence of a head must be balanced by a tail in one of the next two or three tosses

B. If I flip the coin 10 times, it would be almost impossible to obtain 7 heads and 3 tails

C. If I flip the coin many, many times the proportion of heads will be approx. 1/2 and this proportion will tend to get closer and closer to 1/2 as the number of tosses increases

D. Regardless of the number of flips, half will be heads and half tails

E. All of the above

C. If I flip the coin many, many times the proportion of heads will be approx. 1/2 and this proportion will tend to get closer and closer to 1/2 as the number of tosses increases

The collection of all possible outcomes of a random phenomenon is called

A. A census

B. The probability

C. A chance experiment

D. The sample space

E. The distribution

D. The sample space

An assignment of probabilities must obey which of the following?

A. The probability of any event must be a number between 0 and 1, inclusive

B. The sum of all probabilities of all outcomes in the sample space must be exactly one

C. The probability of an event is the sum of the probabilities of outcomes in the sample space in which the event occurs.

D. All three of the above

E. Only A and B

D. All three of the above

If the knowledge that an event A has occurred implies that a second event B cannot occur, the events A and B are said to be

A. Independent

B. Disjoint

C. Mutually exhaustive

D. The sample space

E. Complementary

B. Disjoint

Event A has probability 0.4. Event B has probability 0.5. If A and B are independent, then the probability that both events occur is

A. 0.0

B. 0.1

C. 0.2

D. 0.7

E. 0.9

C. 0.2

Which of the following is true about every random variable

I. It takes on numerical or categorical values

II. It describes the results of a random phenomenon

III. Its behavior can be described by a probability distribution.

A. I only

B. II only

C. III only

D. II and III

E. All three statements are true

D. II and III

Which of the following random variables should be considered continuous?

A. The time it takes for a random chose woman to run 100 meters

B. The number of brothers a randomly chosen person has

C. The number of cars owned by a randomly chosen adult male

D. The number of orders received by a mail-order company in a randomly chosen week

E. None of the above

A. The time it takes for a random chose woman to run 100 meters

Which of the following is not a random variable?

A. The heights of randomly-selected buildings in New York City

B. The suit of a card randomly-selected from a 52 card deck

C. The number of children in randomly-selected household in the US

D. The amount of money won (or lost) by the next person to walk out of a casino in Las Vegas

E. All of the above are random variables

B. The suit of a card randomly-selected from a 52 card deck

Which if the following a true statement?

A. The binomial setting requires that there are only two possible outcomes for each trial, while the geometric setting permits more than two outcomes.

B. A geometric random variable takes on integer values from 0 to n.

C. If X is a geometric random variable and the probability of success is 0.85, then the probability distribution of X will be skewed left, since 0.85 is closer to 1 than to 0

D. An important difference between binomial and geometric random variables is that there is fixed number of trials in a binomial setting, and the number of trials varies in geometric setting

E. The distribution of every binomial random variable is skewed right

D. An important difference between binomial and geometric random variables is that there is fixed number of trials in a binomial setting, and the number of trials varies in geometric setting

Which of the following random variables is geometric?

A. The number of phone calls recieved in a one-hour period

B. the number of times I have to roll a six-sided die to get two 5s

C. The number of digits I will read beginning at a randomly selected starting point in a table of random digits until I find a 7

D. The number of 7s in a row of 40 random digits

E. All four of the above are geometric random variables

C. The number of digits I will read beginning at a randomly selected starting point in a table of random digits until I find a 7

To reduce the variability of estimates from a simple random sample, you should

A. Use a smaller sample

B. Use a larger sample

C. Increase the bias

D. Use a count, not a percent

E. Use a percent, not a count

B. Use a larger sample

According to a recent poll, 27% of Americans get 30 minutes of exercise at least five days each week. Let's

assume this is the parameter value for the population. If you take a simple random sample of 25 Americans

and let (p hat) = the proportion in the sample who get 30 minutes of exercise at least five days per week, is the shape and sampling distribution of (p hat) approx. Normal?

A. No, because n

A. No, because n

A factory produces plate glass with a mean thickness of 4 mm and a standard deviation of 1.1 mm. A simple random sample of 100 sheets of glass is to be measured, and the mean thickness of the 100 sheets X is to be computed. we know the random variable C has approx. a normal distribution because of the

A. Law of large numbers

B. Central Limit Theorem

C. Law of proportions

D. Fact that probability is the long run proportion of times an event occurs

E. Normality of the population distribution

B. Central Limit Theorem