STAT Carmen HW

Bob is interested in examining the relationship between the number of bedrooms in a home and its selling price. After downloading a valid data set from the internet, he calculates the correlation. The correlation value he calculates is only 0.05. What does Bob conclude? -Bob continues his research because even though there is no linear relationship here, there could be a different relationship. -Bob gives up on his research because r = .05 means there is no relationship of any kind between bedrooms and selling price.

Bob continues...

Suppose 35% of the women in a poll of Americans support candidate A for president (and 65% do not.) These results make up what kind of distribution? Marginal distribution of support (yes/no) Conditional distribution of support (yes/no) given women Conditional distribution of women given support (yes/no) None of these answers is correct

Conditional distribution of support (yes/no) given women

The standard deviation has no units. True or False

False

An outlier in a data set can significantly affect the value of the mean but not the median. True or false

True

Suppose your data represent revenues from a group of 20 stores in a retail chain across the country, and revenue is measured in millions of dollars. The standard deviation of this data set would also be measured in millions of dollars. true or false

True

Suppose the equation y = 3.45 - 2.58x represents a valid regression equation and X can be used to predict Y. From this information, we know that X and Y have _____________ correlation.

a negative

What is the most common observational study? -a random sample -an experiment -a survey

a survey

If a residual is negative, then that data point lies _________________ the regression line.

below

Bob wants to estimate the percentage of people who own a dog in his town, and he goes to all the apartment buildings to carry out his survey. He leaves out all the houses in the town. What kind of bias is this? -nonresponse bias -response bias -bias due to under coverage

bias due to under coverage

Which type of graph is best for COMPARING two or more quantitative data sets, a boxplot or a histogram?

box plot

Which type of graph is made from the 5-number summary?

box plot

Suppose the correlation between X =price of a gallon of gasoline and Y = price of a gallon of milk is r = .30 Should we go on and try to make predictions for milk prices using gasoline prices using a straight line? true or false

false

Suppose the correlation between two variables X and Y is .8. That means the correlation between Y and X is -.8. true or false

false

Mike marks down the gas mileage of his two cars every time he fills them up with gas for 6 months straight. At the end he notes that his Mustang gets better mileage than his Corvette. Is this an experiment or an observational study? observational study or experiment

observational

The slices on a pie chart represent relative frequencies. True or False

true

A two-way table allows us to examine the relationship between _____________________ variables.

two categorical

What is the standard deviation of the data set 1, 1, 1, 1?

0

What does SSE stand for

Sum of Squares for Error

Data was collected on amount of rainfall (inches) and amount of corn produced (bushels per acre) for a number of years in Kansas. The output is shown below. Assume the scatter plot looks good. What are the units of slope in this situation? bushels per inch bushels per acre inches per bushel slope has no units

bushels per inch

A listing of all possible values in a data set and how often they occurred is called a data _____________________.

distribution

If the mean of a data set is large, the standard deviation has to be large also. True or False

false

If there are a few very small values in a data set compared to the rest of the data, the mean will be larger than the median. True or False

false

What kind of sample occurs when you put an ad in the newspaper and ask readers to take your survey?

self selected sample

Which is more affected by skewness, the IQR or standard deviation?

standard deviation

Which of the following can never be negative? mean median all of these choices can be negative standard deviation

standard deviation

When a difference in treatment is decided to be due to more than random chance, what do you call the results? -Avoid or minimize bias -Statistically different -Statistically extrapolated -Statistically significant

statistically significant

A researcher is trying to use January temperatures to predict latitude. This means January temperature is the X (independent) variable and latitude is the Y (dependent) variable. true or false

true

Correlation is affected by outliers. true or false

true

If 2 corresponding conditional distributions are different from each other in a two-way table, we know that the variables are related. true or false

true

If you could choose four numbers from 1, 2, 3, 4 and repeated numbers were allowed (such as 1, 1, 3, 2), which set of four numbers would give you the largest standard deviation? (No calculations needed.) 1, 1, 4, 4 No answer text provided. 1, 2, 3, 4 1, 1, 1, 4

1, 1, 4, 4

What should the residual plot look like if the regression line fits the data well? no fan shapes random patterns points fall around the horizontal line Y = 0 all of these choices are correct

all of these choices are correct

If a data set is skewed to the left, how will the mean and median compare?

mean will be less than median

You can have two data sets with the same mean but different standard deviations. True or False

True

As we heard in lecture, the "average distance from the mean" is measured by the __________________________.

standard deviation

The government is interested in cars using less fuel, so they decide to provide a 'gas guzzler tax' for those who own vehicles that get bad gas mileage (low numbers for mpg). What is cutoff for MPG if you want only 25% of the cars to receive this tax?

whatever the value of Q1 is

A __________ distribution summarizes the information from one variable ONLY, without considering ANY information from another variable.

marginal distribution

If you add 10 to every value of a data set, what happens to the standard deviation? -It stays the same -It decreases -it increases

it stays the same

Which of the following distributions must sum to 1? The joint ("and") distribution of seeing the ad (yes/no) and making purchase (yes/no) The conditional distribution of making a purchase (yes/no) given the person saw the ad The marginal distribution of making a purchase (yes/no) All of these choices are correct

all of these choices are correct

Boxplot A and Boxplot B are drawn on the same axes. The box part of Boxplot A is shorter in length than the box part of Boxplot B. What can you tell about the two data sets? -They have to contain the same amount of data. -Boxplot B has to contain more data than Boxplot A. -You cannot tell anything from the information provided. -Boxplot A has to contain more data than Boxplot B

you cannot tell anything from the info provided

A flat histogram (with a line straight across) contains no variability whatsoever, according to our definition. True or False

false

Suppose the correlation between yards rushing and yards passing is .6. That means the correlation between feet rushing and feet passing is .6 x 12 (since you multiply yards by 12 to convert to feet). true or false

false

The median must be one of the numbers in the data set. True or False

false

Your boss gives you the following regression equation. X = square feet and Y = selling price Selling price = $5,240 + $33.80 (Number of Square Feet). Does it make sense to interpret the Y-intercept for this equation? true or false

false

The starting point can affect the way a graph looks. True or false

True

The personnel department keeps records on all employees in a company. Here is the information they keep in one of their data files: Employee identification number Last name First name Middle initial Department Number of years with the company Salary ($) Education Level (high school, some college, or college degree) Age (years) Which of the following combinations of variables would be appropriate to examine with a scatterplot? Salary and Education Level. All of these choices are correct. Education Level and Age. Age and Salary.

Age and salary

Your boss gives you the following regression equation. Selling price = $5,240 + $33.80 (Number of Square Feet). How do you interpret the slope for this equation? As selling price increases by $1, square feet increases by $33.80 As square feet increases by 1, selling price increases by $5,240. As square feet increase by 1, selling price increases by $33.80 As selling price increases by $1, square feet increases by 5,240.

As square feet increase by 1, selling price increases by $33.80

A five number summary contains the min, max, Q1, Q3, and what other value? -All of these answers are correct. -the Median -the 50th percentile -Q2

all of these answers are correct

Which of the following is the X variable in an experiment? -confounding variable -dependent variable, or response -independent variable, or factor

independent variable or factor