Stats 1430 midterm

You can compare two marginal distributions to see if the corresponding two variables are related.

false

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

data distribution

If you add the same positive number to every value of a data set what happens to the standard deviation?

does not change

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

false

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

false

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

false

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

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

true

Correlation is affected by outliers.

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

The slices on a pie chart represent relative frequencies.

true

The starting point can affect the way a graph looks.

true

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

true

Suppose you have 4 data sets whose scatterplots all show possible linear relationships. The four data sets have correlations of -0.10, +0.25, -0.90, and +0.80, respectively. Which of the correlations shows the strongest linear relationship?

-.90

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

0

What is the most common observational study?

A survey

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

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?

Bias due to undercoverage

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?

Conditional distribution of support (yes/no) given women

Which of the following is the X variable in an experiment?

Independent variable, or factor

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

Standard Deviation

What does SSE stand for?

Sum of Squares for Error

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

The mean will be less than the median. left=less

A researcher is trying to predict the linear relationship between January revenue and yearly revenue for her company. The correlation turns out to be .60. How does she interpret this correlation?

There is a moderate positive linear relationship between January revenue and yearly revenue.

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

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?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?

You cannot tell anything from the information provided (can't tell the size of data based on boxplot)

What should the residual plot look like if the regression line fits the data well?

all -> random patterns, no fan shapes, points fall around horizontal line y=0

Which of the following summary measures cannot be directly calculated from a boxplot?

all -> standard deviation, mean, sample size

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

below

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

boxplot

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

boxplot

If you add 10 to every value of a data set, what happens to the standard deviation?

it stays the same

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

marginal

A five number summary contains the min, max, Q1, Q3, and what other value?

q2, 50th percentile, median

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

standard deviation

Which of the following can never be negative?

standard deviation

When a difference in treatment is decided to be due to more than random chance, what do you call the results?

statistically significant

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.

false

The standard deviation has no units.

false

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

a self-selected sample

If variables A and B are related in a certain way in a two way table (with 2 variables), no matter how many other variables you look at in addition to these two, the relationship will always stay the same.

false

In a boxplot you can tell the exact pattern of the data set (beyond just whether the data is skewed or symmetric.)

false

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

false

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.

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

true

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

two categorical

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).

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