Math Unit 2

George needs money to buy a motor scooter. He borrows $1000 from his favorite aunt, who has agreed not to charge him interest. He agrees to pay $50 per month. In a regression model to represent his outstanding debt, the value of the slope will be ____.

-50

A professor has found in the past that students' scores on a certain exam are close to normally distributed with a mean of 78 and a standard deviation of 9. What percentage of the students does she expect to receive less than 60?

2.28

Dan has been saving money each week in a box under his bed. The equation that predicts how much money he has is y^ = 20 + 4x, where x is the number of weeks he has added to his box. This equation tells us that he started with $____.

20

If a variable is normally distributed, what percentage of the data is between −1 standard deviation and 1 standard deviation from the mean?

68%

Approximately ____% of the data is greater than the first quartile. Give your answer in numeral form.

75%

A professor has found in the past that students' scores on a certain exam are close to normally distributed with a mean of 78 and a standard deviation of 9. What is the lowest score that she expects to still be in the top 25%? (Use a whole number.)

84

A variable is normally distributed with a mean of 240 and a standard deviation of 20. What percentage of the values should be between 200 and 280?

95.44

The parameter is a descriptor word or phrase that describes the individuals in a population. True or False

False, A parameter is a number that summarizes information about the entire population. It is not a word phrase describing the individuals.

Two variables are said to be confounded when their effects on the response variable cannot be duplicated.

False, Two variables are said to be confounded when their effects on the response variable cannot be separated from each other. If the effects cannot be duplicated, there is no real relationship.

A(n) _____ is an individual value that falls outside the overall pattern of the data.

Outlier

The graph has two values that are much lower than the rest.

Outliers

What is meant by least-squares line?

The line for which the sum of squared vertical deviations of the data points from the line is as small as possible.

Which of the following is NOT true about a histogram? The labels on both axes are numerical. The height of the columns depends on the number of observations in each class. All of the classes have equal width. The variable graphed can be numerical or qualitative.

The variable graphed can be numerical or qualitative.

The law of large numbers states that as sample size increases, the sample mean gets closer and closer to the population mean. True or False

True

In statistics a variable is:

a characteristic that may take on different values for a group of observations

For any continuous random variable, the probability that the variable takes on a value in a given range is given by a(n)

area.

A variable that places an individual into one of several groups is called a/an _________ variable.

categorical

The following variables are _____. Gender, Hair Color, Eye Color

categorical

The notation nCk is used for _______.

combinations

The correlation coefficient, r, measures the ______ and strength of a linear relationship.

direction

A(n) ______ is an outcome or any set of outcomes of interest in a random process.

event

The researcher randomly assigns the treatments to the individuals in an __________

experiment

In examining a relationship between two variables, the variable used to (hopefully) predict the second is called the ______ variable

explanatory

For random samples of size 9 from a population, the standard deviation of the sample means from all possible samples ________ the population standard deviation.

is less than

The following variables are _____. Age, Height, SAT score

numerical

The average ACT score of all incoming freshmen at a large private university is 27. The number 27 is a ________, because it summarizes information about the university's freshman population.

parameter, It is a parameter because it is a number that summarizes information about the entire population, the population being all incoming freshmen

A variable that has a distribution that can be graphed by a histogram must be _____.

quantitative

If we measured the price of the houses in thousands of dollars instead of dollars (i.e., 97.5 instead of 97,500), which quantity will be unchanged? -r -the y-intercept, a -the slope, b -No quantities will change.

r Changing the unit of measure for either x or y does not change r or r2.

In examining a relationship between two variables, the variable we think represents the outcome of interest is called the ________ variable.

response variable

Discrete random variables have a finite or countable.....

sample space, number of possible values

The graph has two peaks, one on the right and one on the left, with a gap in the middle. This is a description of the _____ of the distribution.

shape

A regression line is expressed as y = a + bx. The quantity telling us how much y changes for a one-unit increase in x is called the ______.

slope

The average number of hours of sleep per night was 9.46 hours for a sample of 104 five to seven year-old children. The number 9.46 is a __________.

statistic, It is a statistic because it is a number that summarizes information from a sample of 104 children.

Before computing the correlation coefficient, r, we need to know ____________.

the mean and standard deviation of both variables.

The regression line is expressed as y = a + bx. What does a in this equation tell us?

the predicted y for x = 0

For which of the following situations would it be appropriate to calculate r, the correlation coefficient? -party affiliation of senators and their vote on presidential impeachment -income for county employees and their respective counties -eye color and hair color of selected participants -time spent studying for statistics exam and score on the exam

time spent studying for statistics exam and score on the exam

A regression line is expressed as y = a + bx. What is the purpose of this equation?

to model how a response variable y changes as an explanatory variable x changes

The values are all between 25 and 61. This is a description of the _____ of the distribution.

variability

A characteristic that takes on different values for a group of observations is called a(n) _____.

variable

A regression line is given as y = a + bx. a in the equation tells us the value of y when ______.

x=0