Chapter 2

Question 1

Purpose of graphs

Answer 1

enable visual comparisons of measurements between groups and expose relationships between different variables

Question 2

Relative Frequency Distribution

Answer 2

describes the fraction of occurrences of each value of a variable

Question 3

Relative frequency

Answer 3

proportion of observations having a given measurement

Question 4

What types of tables and graphs are used for categorical data?

Answer 4

frequency tables/bar graphs

Question 5

What types of tables and graphs are used for numerical data?

Answer 5

frequency tables/histograms

Question 6

Mode

Answer 6

the interval corresponding to the highest peak in the frequency distribution

Question 7

What does a percentile of a measurement specify?

Answer 7

the % of observations less than or equal to it; the remaining observations exceed it

Question 8

Cumulative frequency distribution

Answer 8

graph of all the quantiles of a numerical variable; can be used to look at association between a numerical variable and a categorical variable

Question 9

Cumulative relative frequency

Answer 9

(at a given measurement) the fraction of observations less than or equal to that measurement

Question 10

What type of graph is good for displaying the shape of a single frequency distribution and for detecting outliers?

Answer 10

histograms

Question 11

Contingency table

Answer 11

a frequency table that gives the frequency of occurrence of all combinations of 2 or more categorical variables

Question 12

Grouped bar graph

Answer 12

uses the height of rectangular bars to display the frequency distributions of 2 or more categorical variables

Question 13

Mosaic plot

Answer 13

similar to grouped bar graph but the bars within groups are stacked on top of one another rather than placed side by side

Question 14

Describe and identify an observational study

Answer 14

assignment of treatments is NOT made by the researcher

Question 15

Describe and identify an experimental study

Answer 15

researcher randomly assigns individuals to treatment groups

Question 16

Why are experimental studies more powerful?

Answer 16

They can help determine cause and effect relationships

Question 17

Bin widths

Answer 17

intervals present in histograms

Question 18

How does changing the bins change the histogram?

Answer 18

the spread of the data would look narrower or wider depending on the spread

Question 19

Scatterplot

Answer 19

shows pattern of association between 2 numerical variables; x axis= explanatory variable; y axis= response variable

Question 20

Line graph

Answer 20

used to show ordered series (ex. time); only 1 y measurement for every x

Question 21

Maps

Answer 21

spatial equivalent of line graph; displays a numerical response measurement at multiple locations on a surface; explanatory variable= ordered series (ex. points in space)

Question 22

Zero baseline is essential for what types of graphs?

Answer 22

bar graphs and histograms

Question 23

What are 5 elements of effective graphs?

Answer 23

1. show the data
2. represent magnitudes accurately
3. draw graphical elements clearly, minimizing clutter
4. make displays easy to interpret
5. clearly identify the axes