Ch. 2

Skewed

line contains a "tail"

Relative Frequency

the fraction or percent of the time that an event occurs in an experiment

Symmetry

Left and Right are identical

Identify the different modalities.

Unimodal- 1 hump Bimodal- 2 humps (do not need to be of equal size) Multimodal- 3+ humps (do not need to be of equal size)

Cumulative Relative Frequency

percentage at or below Ex. 2, 5, 9 -> 0.10, 0.25, 0.45

Percentile Rank

percentage of measurements in the distribution below that score value

P%

percentile rank

If the tail of a line is pointing to the right, it is ____ skewed.

positively

Score Value (Given Percentile Rank) Formula

score value = LRL + [(P% x n)/100) -nb]/nw x I

x

scores

I

size of the class Interval - 2, 3, 5, or multiple of 5 - Upper Real Limit - Lower Real Limit

N

sum of all frequencies

Where can n be found?

top of cumulative frequency column or sum of frequency

n

total Number of measurements in the distribution

Score value

value for which you are determining the percentile rank

What does the x-axis indicate?

variable measured

What orientation is the y-axis?

vertical

Central Tendency

what score value represents the center of the distribution

Percentile

when a score is identified by its percentile rank

How do you indicate the sum of all frequencies?

Σ = N =

When working on a Grouped Frequency Distribution Table, always work from ____ to _____.

bottom/top

Where can nb be found?

cumulative frequency column, below x

Variability

degree to which measurements in a distribution differ from one another

Grouped Frequency Distribution Table

each row in the table is a "group" of possible score values rather than a single score

Frequency Distribution Components

- Scores - Meaning - Frequency - Relative Frequency - Cumulative Frequency - Cumulative Relative Frequency

Cumulative Frequency

- the sum of the frequencies for that score and all previous scores - should equal N at top

Score Value (Given Percentile Rank) Process

- use (P5 x n)/100 to find which class interval contains the score at this percentile - once interval is identified, use frequency and cumulative frequency to complete the formula and find the score value

Identify the 2 different types of variability.

1.) Clustered 2.) Spread

What are the 2 types of frequency distribution graphs?

1.) Histograms 2.) Polygons

What are the 3 characteristics of frequency distribution graphs?

1.) Shape 2.) Central Tendency 3.) Variability

Rules for Creating a Grouped Frequency Distribution Table

1.) table should include 8-10 rows (anymore or less would not create clear change on a graph) 2.) class interval range of scores should be 2, 3, 5, or multiple of 5 3.) lowest value of the lowest class interval should be easily divisible by interval size

Percentile Rank (Given a Raw Score) Formula

P% = { [ ( score value - LRL ) / I x nw] + nb} / n x 100

Do not round a score value if it is ____.

continuous

How many steps are in the Percentile Rank (Given a Raw Score) Process?

1

What are the 3 characteristics of shapes on a graph?

1.) Symmetry 2.) Skewed 3.) Modality

Which frequency distribution graph is a bar graph?

Histogram

LRL

Lower Real Limit of the class interval containing the score value

nb

Number of measurements Below the class interval containing the score value

nw

Number of measurements Within the class interval containing the score value

Which frequency distribution graph is a line graph?

Polygon

Which frequency distribution graph is more common?

Polygon because it is easier to see the shape

Cumulative Frequency Formula

age the value to the previous sum Ex. 2, 3, 4 -> 2, 5, 9

Meaning

explain the significance of the scores and/or their category

f

frequency

Where can nw be found?

frequency column

What does the y-axis indicate?

frequency or relative frequency

Relative Frequency Formula

frequency/sum of all frequencies f/N

Class interval

group of possible score values

What orientation is the x-axis?

horizontal

Modality

how many "humps" in a line

Frequency

how many times a certain score occurs within the collected data

Interval size

i

Identify the interval in the range 0-4

i = 5

If we have a group frequency distribution, label x-axis with ____.

midpoint of class intervals (rather than full interval to reduce stretching)

If the tail of a line is pointing to the left, it is ____ skewed.

negatively