Displaying Quantitative Data

Question 1

Distribution

Answer 1

the ______ of a variable gives a) the possible values of the variable b) the frequency or relative frequency of each value

Question 2

Histogram (relative frequency histogram)

Answer 2

uses adjacent bars to show the distribution of values in a quantitative variable. Each bar represents the frequency (or relative frequency) of values falling in an interval of values.

Question 3

Stem-and-leaf display

Answer 3

A stem-and-leaf display shows quantitative data values in a way that sketches the distribution of the data. It’s best described in detail by example.

Question 4

Dotplot

Answer 4

graphs a dot for each case against a single axis

Question 5

Shape

Answer 5

To describe the shape of a distribution, look for a) single v. multiple modes b) symmetry v. skewness

Question 6

Center

Answer 6

a value that attempts the impossible by summarizing the entire distribution with a single number, a “typical” value.

Question 7

Spread

Answer 7

A numerical summary of how tightly the values are clustered around the “center.”

Question 8

Mode

Answer 8

A hump of local high point in the shape of the distribution of a variable. Their apparent locations can change as the scale of a histogram is changed.

Question 9

Unimodal

Answer 9

Having one mode. This is a useful term for describing the shape of a histogram when it’s generally mound-shaped.

Question 10

Bimodal

Answer 10

Distribution with two modes.

Question 11

Multimodal

Answer 11

Distribution with more than two modes

Question 12

Uniform

Answer 12

A distribution that’s roughly flat

Question 13

Symmetric

Answer 13

A distribution where the two halves on either side of the center look approximately like mirror images of each other.

Question 14

Tails

Answer 14

The parts of a distribution that typically trail off on either side. Distributions can be characterized as having long tails (if they straggle off for some distance) or short tails (if they don’t).

Question 15

Skewed

Answer 15

A distribution that’s not symmetric and one tail stretches out farther than the other. Skewed left if longer tail on that side, skewed right when longer tail is there.

Question 16

Outliers

Answer 16

Extreme values that don’t appear to belong with the rest of the data. May be unusual values that deserve further investigation, or maybe just mistakes. Don’t delete them automatically w/o thinking abt them. Can affect many statistical analyses, so always be alerted to them.

Question 17

Timeplot

Answer 17

Displays data that changes over time. Often, successive values are connected with lines to show trends more clearly.