Chapter 2: Frequency Distribution Flashcards
What is the value of ΣX – 1 for the following scores? Scores: 2, 4, 7
a) 10
b) 11
c) 12
d) 13
12
Organizing a set of scores into a table or a graph would be an example of using ______.
a) population statistics
b) sample statistics
c) descriptive statistics
d) inferential statistics
c) descriptive statistics
In a positively skewed distribution, scores with the highest frequencies are _____.
a) on the right side of
on the right side of the distribution
What does N mean, what does it represent?
N is the total frequency (f) added up
N represents the population
What is the proportion/probability equation?
it represents p
p = frequency (f) / population (N)
p= f/N
What is percentage?
f/N x 100
Should always equal 100 when added up
What is relative frequency?
- Proportion
- Looking at an individual score/frequency relative to the whole distribution of scores
How do you calculate the range?
Ex- high score of 94 & low score of 53
(H - L) + 1
(high score - low score) +1
or
High upper limit for the high score - Lower upper limit for the low score
Ex: (94-53) +1 –> 42
or
94.5 - 52.5 = 42
What does dividing the range by width give you?
the interval
Positively Skewed Distributions
occur when there is a…
(5 pts)
- Cluster of lower scores
- The smaller more spread-out tail will be on the right
- Scores with higher distribution appear on the left
- Fewer high scores
- “Floor effect”
Negatively Skewed Distributions
occur when there is a…
(5 pts)
- Cluster of higher scores
- The smaller more spread out tail will be on the left
- Scores with higher distribution appear on the right
- Fewer small scores
- “Ceiling effect”
Start interval with…
a multiple of the width
ex. if width is 5, start with a multiple of 5 to start the interval
ex. 5-9 not 7-11
What type of variable and graph represents a nominal scale?
Variable : discreet
Graph: only a bar graph
What type of variable and graph represents a
ordinal scale?
Variable: continuous
Graph: only a histogram
What type of scale(s) is represented by a histogram and/or polygon?
Interval and ratio scales
What is the difference between a nominal scale and ordinal scale? Provide examples
Nominal scale:
-no quantitative distinctions
-labels and categorize
Ex- eye color, diagnosis, control & experimental
Ordinal scale:
-categorizes observations
-categories organized by size or magnitude
Ex- ranks in class, S,M, L, XL, Olympian metals
Does a bar graph with discrete variables have real limits?
no, continuous variables do
What is a frequency distribution?
It counts the number of times each score is received
Name:
- Shows how many times each value occurred on the variable
- Lists the count for each of the different values; frequency of occurrence (f)
- Provides other info (proportions, percentages)
Frequency tables
What are important distinctions about a bar graph?
- Discrete variables
- Measured on a nominal scale
- The graph is drawn with space between the bars
Name the graph:
- Continuous variables
- Includes RL
- Could have fractions/decimals
Histogram
Name the graph:
-Can have interval for X value
-Center a dot over the midpoint of the class interval
Polygon
Name:
What shape of frequency distribution ?
-Having one peak
Unimodal
Name:
Approximately equal numbers of observations above and below the middle
Symmetrical frequency distribution
Name:
-One side is more spread out than the other, like a tail
-Direction of the skew ( right or left/ pos or neg)
Skewed frequency distribution
Name:
What shape of frequency distribution ?
-Having two peaks
Bimodal
Name:
What shape of frequency distribution ?
-Having two or more peaks
multimodal
Name:
What shape of frequency distribution ?
-Having no peaks
Rectangular
Complete the sentence:
When we describe the shape of a distribution, how flat or peaked it is describes its…
Kurtosis
Name:
Types of Kurtosis:
- Are tall and peaked
Leptokurtic distributions
Name:
Types of Kurtosis:
- Are the ideal example of the normal distribution, somewhere between the leptokurtic and platykurtic
Mesokurtic distributions
Name:
Types of Kurtosis:
- Are broad and flat
Platykurtic distributions
What are the 4 particular characteristics of “the normal curve”?
- Bell-shaped
-Unimodal
-Symmetrical - Exactly half of the scores above the mean & exactly half of the scores below the mean
-Average tails
