Chapter 3: Displaying Data

Question 1

Frequency (f) Distribution

Answer 1

• Value of dependent variables are tabled/ plotted against their frequency of occurrence
• -Follows a logical order
• Summary of a set of data showing the frequency of each value (or range of values) of a variable

Question 2

Real Lower Limit

Answer 2

Point halfway b/w bottom of one interval & top of the one below it

Question 3

Real Upper Limit

Answer 3

Point halfway b/w top of one interval & bottom of the one above it

Question 4

Midpoint

Answer 4

Center of the interval; average of upper & lower limits

Question 5

Histogram

Answer 5

Graph where a rectangle is used to rep the freq of observations w each interval; data is collapsed into intervals

Question 6

Stem & Leaf Plot

Answer 6

• Graphical data presenting original quantitative data arranged in a histogram
• -Retains both individual values & the frequency of those values
• -Helps us visualize the shape of a distribution
• Items are “binned”

Question 7

Exploratory Data Analysis (EDA)

Answer 7

Set of techniques developed to present data in visually meaningful ways
-Ie. stem & leaf plot

Question 8

Leading Digits

Answer 8

Leftmost digits of a #

-Most significant

Question 9

Stem

Answer 9

Vertical axis of display containing the leading digits

Question 10

Trailing Digits

Answer 10

Digits to the right of the leading digits

-Less significant

Question 11

Leaves

Answer 11

Horizontal axis of display containing all trailing digits

Question 12

Drawbacks of Stem & Leaf Plot

Answer 12

For some data sets, it’ll lead to course grouping, therefore including too many leaves for each stem

Question 13

Bar Graph

Answer 13

Graph in which the freq of occurrence of different values of X is represented by the height of a bar

• Hard to read graphs b/w the X & Y axis: don’t consistently or strictly represent the ie. independent variable
• -Lots of graphs & variation

Question 14

Line Graph

Answer 14

Y values corresponding to different X values are connected by a line

Question 15

Symmetric/ Normal Distribution

Answer 15

• Same shape on both sides & center

- Distribution can be bisected at the mean & looks like mirror image

Question 16

Bimodal Distribution

Answer 16

Two distinct peaks

Question 17

Modal Distribution (Modality)

Answer 17

of meaningful peaks in a frequency of the data

Question 18

Negatively Skewed

Answer 18

Distribution which trails off to the left

Question 19

Positively Skewed

Answer 19

Distribution which trails off to the right

Question 20

Skewness

Answer 20

• Measure of the degree to which a distribution is assymetrical
• Extent to which a distribution of scores deviates from symmetry
• More scores are clustered in one end (tail) than the other

Question 21

Why Plot Data?

Answer 21

• Means of communicating/ simplifying otherwise ambiguous data
• -Despite popular belief, data can’t speak for itself
• We can look more easily at the global picture of data

Question 22

Histogram: Frquency

Answer 22

How many events do we see in each category (X)?

Question 23

Histogram: Relative Frequency (Rel f)

Answer 23

Of all the events, what proportion of the events happened in the category (X)?

Question 24

Histogram: Cumulative Frequency (Cum f)

Answer 24

• How many events occurred over a # of categories (X)?

- Start by adding up all categories above the one you’re working with (this makes it cumulative)

Question 25

Histogram: Cumulative Relative Frequency (Cum Rel f)

Answer 25

-Of all the events, what proportion of the events happened UP TO category (X)?

Question 26

What can we us Descriptive Statistics to show?

Answer 26

- Shape of distribution (ch3) - Center of distribution (ch4) - Width of distribution: the scatter of values around the center (ch5)