Unit 1 Analyzing Data Flashcards

What is a population?

The entire group we want information about.

What is a sample?

The group actually observed or measured.

What is a variable?

A characteristic recorded for each observational unit.

What is a categorical variable?

A variable that places individuals into groups or categories.

What is a quantitative variable?

A numerical variable for which arithmetic operations have meaning.

What is an explanatory variable?

A variable that may help explain or predict changes in another variable.

What is a response variable?

The outcome variable being measured or predicted.

What is relative frequency?

The proportion or percent of observations in a category.

What is a marginal relative frequency?

A relative frequency for one variable without conditioning on the other variable.

What is a joint relative frequency?

A relative frequency for a specific combination of two categories.

What is a conditional relative frequency?

A relative frequency calculated within a particular group or condition.

When are two categorical variables associated?

When knowing the value of one variable helps predict the value of the other.

What does SOCS stand for when describing a quantitative distribution?

Shape, Outliers or unusual features, Center, Spread.

What must be included with SOCS in an AP Statistics response?

Context. Describe what the values actually represent, including appropriate units when available.

What does resistant mean?

A statistic is resistant if extreme values or outliers do not strongly affect it.

Which measures of center and spread are resistant?

Median and IQR.

Which measures of center and spread are nonresistant?

Mean and standard deviation.

What is the mean?

The arithmetic average of the observations.

What is the median?

The middle value when the observations are put in order.

What does standard deviation measure?

The typical distance of the observations from the mean.

How should you interpret standard deviation in context?

The values typically vary about ___ units from the mean of ___.

What is the interquartile range, or IQR?

Q3 minus Q1. It measures the spread of the middle 50 percent of the data.

For a distribution skewed right, how do the mean and median usually compare?

The mean is usually greater than the median.

For a distribution skewed left, how do the mean and median usually compare?

The mean is usually less than the median.

For a roughly symmetric distribution without strong outliers, which measures are usually appropriate?

Mean and standard deviation.

For a skewed distribution or one with strong outliers, which measures are usually appropriate?

Median and IQR.

What does it mean for a value to be at the 80th percentile?

About 80 percent of the observations are at or below that value.

What is a z-score?

The number of standard deviations a value is above or below the mean.

How do you interpret a positive z-score?

The value is above the mean.

How do you interpret a negative z-score?

The value is below the mean.

How should you interpret a z-score of -1.7 in context?

The value is 1.7 standard deviations below the mean.

Why are z-scores useful for comparison?

They allow us to compare relative position in different distributions or distributions with different units.

What happens to the mean when the same constant is added to every value?

The mean increases by that constant.

What happens to the standard deviation when the same constant is added to every value?

The standard deviation does not change.

What happens to the mean when every value is multiplied by a positive constant?

The mean is multiplied by that constant.

What happens to the standard deviation when every value is multiplied by a positive constant?

The standard deviation is multiplied by that constant.

What happens to the shape of a distribution when every value is transformed by adding a constant or multiplying by a positive constant?

The shape stays the same.

What are the mean and standard deviation of a standardized z-score distribution?

Mean 0 and standard deviation 1.

When comparing two quantitative distributions, what should your response discuss?

Compare shape, unusual features, center, and variability in context.

What is a strong AP Statistics comparison statement?

Make a direct comparison between the groups and support it with features or numerical values from the distributions.