AP Stats 1

Histogram

A histogram is made up of columns plotted on a graph The columns are positioned over a label that represents a continuous, quantitative variable . The height of the column indicates the size of the group defined by the column label.

Dot Plot

A dotplot is a type of graphic display used to compare frequency counts within categories or groups. As you might guess, a dotplot is made up of dots plotted on a graph. The dots are stacked in a column over a category, so that the height of the column represents the relative or absolute frequency of observations in the category.

Frequency

A frequency count is a measure of the number of times that an event occurs.

Stem Plot

A stemplot is used to display quantitative data, generally from small data sets (50 or fewer observations). In a stemplot, the entries on the left are called stems; and the entries on the right are called leaves.

Continuous Variable

If a variable can take on any value between its minimum value and its maximum value, it is called a continuous variable; otherwise, it is called a discrete variable.

Discrete Variable

If a variable can take on any value between its minimum value and its maximum value, it is called a continuous variable; otherwise, it is called a discrete variable.

Statistic

a characteristic of a sample. Generally, a statistic is used to estimate the value of a population

Parameter

a measurable characteristic of a population, such as a mean or a standard deviation

Sample

a sample refers to a set of observations drawn from a population.

Census

a study that obtains data from every member of a population.

Box Plot

a type of graph used to display patterns of quantitative data A boxplot splits the data set into quartiles. The body of the boxplot consists of a "box" (hence, the name), which goes from the first quartile (Q1) to the third quartile (Q3). Within the box, a vertical line is drawn at the Q2, the median of the data set. Two horizontal lines, called whiskers, extend from the front and back of the box. The front whisker goes from Q1 to the smallest non-outlier in the data set, and the back whisker goes from Q3 to the largest non-outlier.

Variable

a variable has two defining characteristics: A variable is an attribute that describes a person, place, thing, or idea. - The value of the variable can "vary" from one entity to another.

Case/Individual

Cases are nothing but the objects in the collection. Each case has one or more attributes or qualities, called variables which are characteristics of cases.

Relative Frequency

To compute relative frequency, one obtains a frequency count for the total population and a frequency count for a subgroup of the population. The relative frequency for the subgroup is: Relative frequency = Subgroup count / Total count

Qualitative or Categorical Variable

Variables can be classified as categorical (aka, qualitative) or quantitative (aka, numerical).

Quantitative Variable

Variables can be classified as categorical (aka, qualitative) or quantitative (aka, numerical). Categorical. Categorical variables take on values that are names or labels. The color of a ball (e.g., red, green, blue) or the breed of a dog (e.g., collie, shepherd, terrier) would be examples of categorical variables. Quantitative. Quantitative variables are numerical. They represent a measurable quantity. For example, when we speak of the population of a city, we are talking about the number of people in the city - a measurable attribute of the city. Therefore, population would be a quantitative variable.

Descriptive Statistics

brief descriptive coefficients that summarize a given data set, which can be either a representation of the entire or a sample of a population. Descriptive statistics are broken down into measures of central tendency and measures of variability (spread)

Estimation

estimation refers to the process by which one makes inferences about a population, based on information obtained from a sample.

Distribution

is a listing or function showing all the possible values (or intervals) of the data and how often they occur. When a distribution of categorical data is organized, you see the number or percentage of individuals in each group.

Two Way Table

is a useful tool for examining relationships between categorical variables. The entries in the cells of a two-way table can be frequency counts or relative frequencies

Variability

lack of consistency or fixed pattern; liability to vary or change.

inferential statistics

random sample of data taken from a population to describe and make inferences about the population

Population

the total set of observations that can be made.