PSYC*1010 Chapter 2: Frequency Distributions

Question 1

What is a frequency distribution?

Answer 1

An organized tabulation of the number of individuals located in each category on a scale of measurement

Question 2

What are three things that frequency distributions provide information about?

Answer 2

• Whether scores are generally high or low
• Whether scores are concentrated in one area or spread out across the entire scale
• The location of any individual score relative to others in the set

Question 3

What two elements are presented in both frequency distribution tables and frequency distribution graphs?

Answer 3

• The set of categories that make up the original scale of measurement
• A record of the frequency/ number of individuals in each category

Question 4

How can the number of participants be calculated with the information provided by a frequency distribution?

Answer 4

By adding all the frequencies in a distribution

Question 5

How is the sum of scores obtained from a frequency distribution?

Answer 5

Each X value is multiplied by its frequency and the products are totalled

Question 6

What are the two most common measures that describe distribution of scores and can be incorporated into a frequency distribution table?

Answer 6

Proportion and percentage

Question 7

What does proportion measure?

Answer 7

The fraction of the total group associated with each score

Question 8

How is proportion most frequently expressed?

Answer 8

Proportion is most frequently expressed as a decimal rather than a fraction

Question 9

How is the proportion of a score in a frequency distribution calculated?

Answer 9

Proportion of a score is calculated by dividing its frequency by the total number of scores

Question 10

How is the percentage of a score in a frequency distribution calculated?

Answer 10

The percentage associated with each score is the product of the proportion multiplied by 100

Question 11

What is a grouped frequency distribution?

Answer 11

A frequency distribution where scores are grouped into intervals rather than listed as individual values

Question 12

What is range, and how is it calculated?

Answer 12

• Range: the distance between the absolute highest and lowest points in a distribution
• Range = highest score - lowest score

Question 13

What is a class interval?

Answer 13

The group of scores in a grouped frequency distribution

Question 14

What are the five guidelines for creating class intervals?

Answer 14

• There should be about 10 intervals
• The width should be a relatively simple number
• The bottom score of each interval should be a multiple of the width
• All intervals should be the same width
• The intervals should completely cover the range of scores with no gaps or overlaps

Question 15

How are the sizes of class intervals determined?

Answer 15

Calculate the (range + 1)/10 and chose a convenient interval size as close to that value as possible

Question 16

What type(s) of limits do continuous variables have?

Answer 16

• Real limits
• Apparent limits

Question 17

What are the apparent limits of a class interval?

Answer 17

The score values that appear to be the lowest and highest of an interval

Question 18

What are the real limits of a class interval?

Answer 18

The upper real limit of the first score in a class interval and the lower real limit of the last score in a class interval

Question 19

When are real limits used to describe class intervals?

Answer 19

When measuring and organizing continuous variables

Question 20

What is the abscissa of a graph?

Answer 20

The x-axis

Question 21

What is the ordinate of a graph?

Answer 21

The y-axis

Question 22

What are two guidelines that help avoid creating misleading graphs?

Answer 22

• The point of intersection of both axes has a score of zero
• The y-axis is approximately two-thirds to three-quarters the length of the x-axis

Question 23

What is a histogram?

Answer 23

• A graph showing a bar above each score or interval corresponding to their frequencies
• There are no gaps between bars

Question 24

What do the heights and widths of bars in histograms correspond to?

Answer 24

• Height = Frequency
• Width = class interval size, extending to real limits

Question 25

What is a modified histogram?

Answer 25

Instead of drawing a bar above each score, a stack of "blocks" is used to represent the number of individuals

Question 26

T or F: Modified histograms can be used as a substitute for regular histograms.

Answer 26

- False - A modified histogram is not a substitute for an accurately drawn histogram with two labelled axes

Question 27

What is a polygon?

Answer 27

A graph consisting of a line that connects a series of dots

Question 28

What does the height of a dot in a polygon correspond to?

Answer 28

The height of each dot placed above intervals/scores corresponds to the frequency of that interval/score

Question 29

How is nominal and ordinal data typically displayed?

Answer 29

A bar graph

Question 30

What is a bar graph?

Answer 30

- A graph showing a bar above each score or interval corresponding to their frequencies - There are gaps between adjacent bars

Question 31

What do the spaces between adjacent bars in a bar graph represent when displaying nominal data?

Answer 31

For a nominal scale, the space between bars emphasizes that the scale consists of separate and distinct categories

Question 32

What do the spaces between adjacent bars in a bar graph represent when displaying ordinal data?

Answer 32

For an ordinal scale, the space between bars are present because it cannot be assumed that all categories are the same size/have the same sized intervals

Question 33

What are the two special features of graphs for population distributions?

Answer 33

- Relative frequencies - Smooth curves

Question 34

What is a relative frequency?

Answer 34

A proportion of the total distributor rather than the absolute frequency

Question 35

When are relative frequencies used?

Answer 35

When the total number of individuals is unknown for each category

Question 36

How can relative frequencies be presented/ displayed?

Answer 36

By using a relative frequency graph that does not display absolute numbers, simply the proportions of a category relative to each other

Question 37

What does a smooth curve demonstrate?

Answer 37

The relative changes that occur from one score to the next in a population

Question 38

What are the characteristics of a normal distribution curve?

Answer 38

Symmetrical, with the greatest frequency in the middle and relatively smaller frequencies toward either extreme

Question 39

Which three characteristics completely describe any distribution?

Answer 39

- Central tendency - Variability - Shape

Question 40

How is the shape of a distribution technically defined?

Answer 40

By an equation that describes the exact relationship between each X and Y value on the graph

Question 41

How is the shape of a distribution classified?

Answer 41

The shape of nearly all distributions can be classified as either symmetrical or skewed

Question 42

What is a symmetrical distribution?

Answer 42

If a vertical line was drawn through the distribution curve, each side would be a mirror image of the other

Question 43

What is a skewed distribution?

Answer 43

Occurs when the scores pile up toward one end of the scale and taper off gradually at the other end

Question 44

What is the tail of distribution?

Answer 44

The section where the scores taper off toward one end of a distribution

Question 45

What does a positively skewed distribution look like?

Answer 45

The tail points toward the positive end of the x-axis (on the right-hand side)

Question 46

What does a negatively skewed distribution look like?

Answer 46

The tail points toward the negative end of the x-axis (on the left-hand side)

Question 47

What is the floor effect?

Answer 47

A situation in which a constraint prevents a variable from taking values below a certain point

Question 48

How might the floor effect influence distribution?

Answer 48

It may lead to a positively skewed distribution

Question 49

What is the ceiling effect?

Answer 49

A situation in which a constraint prevents a variable from taking on values above a given number

Question 50

How might the ceiling effect influence a distribution?

Answer 50

It may lead to a negatively skewed distribution

Question 51

What are stem and leaf displays?

Answer 51

A technique for organizing data that requires each score be separated into two parts

Question 52

What do the "stem" and "leaf" in a stem and leaf display represent?

Answer 52

- Stem: the first digit(s) of a score - Leaf: the last digit of a score

Question 53

What does each stem in a stem and leaf display correspond to?

Answer 53

Each stem corresponds to a class interval

Question 54

What does the number of leafs in a stem and leaf display correspond to?

Answer 54

The number of leafs shows the frequency associated with each stem

Question 55

What is the advantage of a stem and leaf display over a traditional grouped frequency distribution?

Answer 55

Stem and leaf displays allow you to identify each individual score in the data

Question 56

What factors need to be considered when determining the type of statistical analyses needed in a study?

Answer 56

- The type of study (correlational, experimental, quasi-experimental) - What type of variables are being used (nominal, ordinal, interval, ratio)