AP Stats Midterm
(T/F) Selection bias occurs only if volunteers are used in a study
T
Event A has probability 0.4. Event B has probability 0.5. If A and B are disjoint, then the probability that both events occur is
0.0
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
0.2
A basketball player makes 160 out of 200 free throws. We would estimate the probability that the player makes his next free throw to be
0.8
Suppose we roll two six-sided dice, one red and one green. Let A be the event that the number of spots showing on the red die is three or less and B be the event that the number of spots showing on the green die is three or more. P(AandB)=
1/3
A researcher wishes to determine whether the rate of water flow over an experimental soil bed can be used to predict the amount of soil washed away. In this study, the explanatory variable is
rate of water flow
If the mean is larger than the median, then the data is skewed _________
right
p hat
sample proportion of success
s^2
sample variance
sigma
summation
The collection of all possible outcomes of a random phenomenon is called
the sample space
In designing an experiment, blocking is used
to reduce variation
A poker player is dealt poor hands for several hours. He decides to bet heavily on the last hand of the evening on the grounds that after many bad hands he is due for a winner. Is he right or wrong?
wrong
In the equation of a straight line, y-a+bx, a is the _______________ and b is the ____________
y intercept, slope
A study is conducted to determine if one can predict the yield of a crop based on the amount of fertilizer applied to the soil. The response variable in this study is
yield of the crop
(T/F) The median and the 50th percentile are the same number
T
(T/F) Two events are said to be disjoint or mutually exclusive when they have no outcomes in common
T
an observation is an extreme outlier if it is more than _________ from the closest end of the box
3IQR
Suppose we roll two six-sided dice, one red and one green. Let A be the event that the number of spots showing on the red die is three or less and B be the event that the number of spots showing on the green die is three or more. P(AuB)=
5/6
(T/F) The probability of an event E can always be computed using the formula P(E)=number of outcomes favorable to E/number of outcomes in the sample space
T
(T/F) The quantity (square root of number of observations) often gives a rough estimate of the appropriate number of intervals in a histogram
T
(T/F) The slope of the least squares line is the average amount by which y increases as x increases by one unit
T
(T/F) The standard deviation about the least squares line is roughly the typical amount by which an observation deviates from the least squares line
T
(T/F) The value of r is affected by extreme values
T
(T/F) If on average y increases as x increases, the correlation coefficient is positive
T
(T/F) If r is close to 1, then the points lie close to a straight line with a positive slope
T
(T/F) If r=1, then the points lie close to a straight line that slopes upward
T
(T/F) If the person measuring the response is aware of the treatment assigned to the subject, but the subject is unaware, a single-blinding is being used
T
(T/F) In bivariate data, the response variable is y and the explanatory variable is x
T
(T/F) One disadvantage of using the mean as a measure of center for a data set is that its value can be affected by the presence of even a single outlier in the data set
T
All freshmen at a university are enrolled in 1 of 30 sections of a seminar course. A researcher selects 4 sections of the seminar course at random from the 30 sections and all the students in the 4 selected sections are included in the sample. What type of sampling is this?
Cluster sampling
A university teacher obtains a sample of students at the university by using the 85 students enrolled in her Psychology class. What type of sampling is this?
Convenience sampling
(T/F) When the shape of a distribution has values along the vertical axis all falling roughly on a horizontal line, that distribution is called flat
F
In one study, 100 subjects who had been long-time niacin takers had their cholesterol levels compared with those of 100 people who had never taken niacin. in a second study, 50 subjects were randomly chosen to receive niacin and 50 were given a placebo. What kinds of studies/experiments were these?
First was observational study, second was controlled experiment
I toss a penny and observe whether it lands heads or tails up. The probability of heads is 1/2 and the probability of tails is 1/2. This means that:
If I flip the coin enough times, the proportion of heads will get closer to 1/2
(T/F) Pearson's correlation coefficient, r, does not depend on the units of measurement of the two variables
T
(T/F) Population correlation coefficient (p) is the measure of how strongly the x and y values in an entire population of (x,y) pairs are linearly related to one another
T
(T/F) A data set is multivariate if it consists only of numeric variables
F
(T/F) A r value of -.7 represents a strong negative correlation
F
(T/F) A simple random sample of size n is any sample that is selected in a manner that guarantees each individual in the population an equal chance of selection
F
(T/F) A study is an observational study if the investigator observes the behavior of a response variable after one or more explanatory variables have been manipulated
F
(T/F) Any collection of possible outcomes of a chance experiment is called a sample space
F
(T/F) Blocking does not help to filter out the effect of extraneous factors
F
(T/F) Data representing the height of tomato plants is considered to be quantitative and discrete
F
(T/F) Dotplots cannot convey information about the extent to which the data values spread out
F
(T/F) If a distribution of data is symmetric, the mean is always less than the median
F
(T/F) If there are no outliers a skeletal and modified boxplot can differ in the length of the box, but not in the whisker lengths
F
(T/F) If two events, A and B, are disjoint, then P(A and B)=P(A)xP(B)
F
(T/F) In a well-designed experiment, the explanatory variables are confounded whenever possible
F
(T/F) Increasing sample size will eliminate bias
F
(T/F) Methods for organizing and summarizing data make up the branch of statistics called inferential statistics
F
(T/F) Response bias can occur if responses are not actually obtained from each of the individuals selected for inclusion in the sample
F
(T/F) Stem and leaf plots are an inappropriate method for displaying quantitative data
F
(T/F) Stratified sampling does not involve simple random sampling
F
(T/F) The classical view of probability is based on the Law of Large Numbers
F
(T/F) The coefficient of determination is always between -1 and 1
F
(T/F) The coefficient of determination is negative when y decreases as x increases
F
(T/F) The entire collection of individuals or objects about which information is desired is called a sample
F
(T/F) The event "A or B" consists of all the outcomes in both of the events
F
(T/F) The mean is the middle value of an ordered data set if the number of observations si odd or the average of the middle two values of an ordered data set if the number of observations is even
F
(T/F) The median is always greater than the mean
F
(T/F) The middle quartile separates the bottom 25% of a distribution of data from the top 25%
F
(T/F) The relative frequency for a particular category is the number of times the category appears in the data set
F
(T/F) The shape of a distribution that has the majority of values to the left is considered to be skewed to the left
F
(T/F) The value of Pearson's r is always between 0 and 1
F
(T/F) The variance is the positive square root of the standard deviation
F
(T/F) Two events are independent if they cannot occur simultaneously
F
(T/F) Two events, E and F, are independent if P(E|F)=P(F|E)
F
(T/F) Relative frequency histograms display the percent or proportion of data points that fall into each bar
T
There are three children in a room, ages three, four, and five. If a four year old enters the room, what happens to the mean age and variance?
Mean age stays the same, variance decreases
A central concern in an observational study is:
Obtaining a sample that is representative of the population of interest
(T/F) The interquartile range is resistant to the effect of outliers
T
A researcher writes the name of each senior on a slip of paper and randomly draws names. What type of sampling is this?
Simple random sampling
An experiment was set up where one classroom used a new software program and another used the old program. The students in both classes were tested before and after using the software. What are the treatments in this experiment?
Software
To obtain a sample of students, faculty, and staff at a university, a researcher randomly selects 50 faculty members from a list of faculty, 100 students from a list of students, and 30 staff members from a list of staff. What type of sampling is this?
Stratified sampling
To obtain a sample of those attending a basketball game, a researcher selects the 24th person through the door. Then every 50th person after that is also included in the sample. What type of sampling is this?
Systematic sampling
(T/F) A chance experiment is any activity or situation in which there is uncertainty concerning which of two or more possible outcomes will result
T
(T/F) A graphical display of data that shows the cumulative counts cross each of the possible data values or ranges of data values is a cumulative frequency histogram
T
(T/F) A placebo is designed to be identical in appearance to the treatment of interest, but contains no active ingredients
T
(T/F) A primary use of inferential statistics involves generalizing from a sample to a population
T
(T/F) A variable is a characteristic whose value may change from one observation to another
T
(T/F) An event consisting of exactly one outcome is called a simple event
T
(T/F) An outlier is "extreme" if it is more than 3.0iqr away from the nearest quartile
T
(T/F) Bar charts are an easy way to compare categories
T
(T/F) Bar charts should be used with categorical, not numerical, data
T
(T/F) Bar graphs are an inappropriate method for displaying quantitative data
T
(T/F) Blocking is used to account for the effects of some extraneous factors
T
(T/F) Clusters are non-overlapping subgroups of a population that have been identified as homogeneous
T
(T/F) Correlation does not imply causation
T
(T/F) Data are discrete if the possible values are isolated points on the number line
T
(T/F) Dotplots work best for reasonably small sized numerical data sets
T
(T/F) For any given data set, the median must be greater than or equal to the lower quartile and less than or equal to the upper quartile
T
(T/F) Histograms show the overall shape, center, and spread of the distribution of data
T
In a study subjects were randomly given either 500 or 1000 milligrams of vitamin C daily and the number of colds they came down with was noted. In another study people responded to a questionnaire about the average numbers of sleep and colds they had during winter. What kinds of studies/experiments were these?
The first was an experiment without a control group, the second was an observational study
The correlation coefficient measures
The strength of the linear relationship between two variables
An experiment was set up where the teacher in one classroom used a new software program and another used the old program. The students in both classes were tested before and after using the software. What variable is confounded with the treatments in this experiment?
The teacher
If the largest value of a data set was changed from 9.1 to 13.2, the mean and median would:
increase and stay the same
Suppose we roll two six-sided dice, one red and one green. Let A be the event that the number of spots showing on the red die is three or less and B be the event that the number of spots showing on the green die is three or more. The events A and B are
independent
A value of r=-.70 indicates a ________________ ______________ relationship between x and y
moderate negative
If you are given a data set with a mean of 3.5 and a median of 5, you can say that the histogram is:
negatively skewed
A stack of 4 cards contains 2 red cards and 2 black cards. I select 2 cards, one at a time, and do not replace the first cared before selecting the second card. A is the event that the first card is red and B is the event that the second card is red. The events A and B are
not independent, not disjoint
u
population mean
o
population standard deviation
o^2
population variance
The proportion of variation explained by a linear relationship x and y is
r^2