AP Stats: U1A - Categorical Variables and Displaying Distributions with Graphs

What is an individual in the context of statistics?

an object described by a set of data, which may be people, animals, or things.

What defines a categorical variable?

places an individual into one of several groups or categories.

What is a quantitative variable?

takes numerical values for which arithmetic operations such as adding and averaging make sense.

What does the distribution of a variable tell us?

what values the variable takes and how often those values occur.

What does SOCS stand for when describing the overall pattern of a distribution?

Spread, Outliers, Center, Shape.

How do you determine if there are outliers in a dataset?

if an individual observation that falls outside the overall pattern of the graph.

What indicates a symmetric distribution?

the mean is equal to the median.

What indicates a left-skewed distribution?

the mean is less than the median.

What indicates a right-skewed distribution?

the mean is greater than the median.

What is a time plot?

graphs each observation against the time at which it was measured.

How do you calculate the mean of a set of observations?

Add all the values together and divide by the number of observations.

What is the median in a data set?

the midpoint of the distribution, with half the observations smaller and half larger.

What does the five-number summary include?

the minimum, Q1, median, Q3, and maximum.

How is the interquartile range (IQR) calculated?

Q3 minus Q1.

What is the outlier criterion based on the IQR?

if number falls more than Q3+1.5(IQR) or lower than Q1—1.5(IQR)

What is a boxplot?

a graph of the five-number summary with outliers plotted individually.

How is standard deviation defined?

the average of the squares of the deviations of observations from their mean.

What formula is used to calculate the sample standard deviation?

s = sqrt(sum of (xi - mean)^2 / (n - 1))