Ch. 2 : Picturing Variation w/ Graphs

Question 1

Bar Chart

Answer 1

This displays counts of each category next to each other for easy comparison

Question 2

Relative frequency bar chart

Answer 2

displays relative proportions of each category

Question 3

Side-by-Side Bar Chart

Answer 3

displays two categorical variables graphically

Question 4

Description of Categorical Distributions

Answer 4

Mode: category that occurs most frequently (or w/ highest frequency) - the “typical” outcome
Variability or Diversity: if distribution has many observations in many diff categories the variability is high (if observ.s fall into same category then variability is low

Question 5

Stem and Leaf Plot

Answer 5

divides each observation into a “stem” and “leaf”

Question 6

Dot Plot

Answer 6

places a dot along an axis for each case in the data

Question 7

Histogram

Answer 7

displays the number of cases in each bin
(bin widths are personal choice)
Horizontal axis: numerical
Vertical axis: frequency

Question 8

Relative Frequency Histogram

Answer 8

the vertical axis represents relative frequencies or percents

• used when have 2 hist.s w/ largely diff frequencies
• find rel freq by dividing frequency by sample

Question 9

Difference between Bar Charts and Histograms

Answer 9

Bar Chart: display categorical/ bar widths mean nothing/ bars don’t have to touch
Histogram: display numerical/ bar widths mean something/ bars must touch

Question 10

Describing Numerical Distributions

Answer 10

Describe with:

Shape, Center, Spread

Question 11

Shape

Answer 11

Unimodal distribution (one peak)
Bimodal distribution (two peaks)
or uniform distribution (none)
-Symmetric or skewed?
-Extreme values: outliers

Question 12

Center

Answer 12

Has a typical value

Question 13

Spread

Answer 13

describes how spread out the data is from the center

• when data close to the center, small spread
• when data far from center, spread is large