Chapter 3

Question 1

Enumeration

Answer 1

Listing all points in a data set.

Question 2

Tabular frequency distribution

Answer 2

A table that lists the numerical values of a variable in a logical order along with frequency of each value.

Question 3

Frequency

Answer 3

Usually abbreviated ‘f’ is the number of times a particular value of the variable occurs.

Question 4

How does a tabular frequency distribution show the values of a variable?

Answer 4

In order with largest value first.

Question 5

What is another name for a grouped frequency distribution?

Answer 5

Frequency distribution using class intervals.

Question 6

Grouped frequency distribution

Answer 6

A frequency distribution with adjacent values of the variable grouped together. The use of class intervals generally makes a frequency distribution easier to understand. Class intervals must be of the same width and it is generally desirable to have between 6 and 20 intervals.

Question 7

What are the six steps for creating a grouped frequency distribution?

Answer 7

1. Find the range of scores (highest score minus lowest score).
2. Make a preliminary choice of the desired number of class intervals.
3. Determine the interval width by dividing the range of by the number of class intervals. Round the interval width in either direction to an even number.
4. Determine the lower limit of the lowest interval.
5. Prepare a list of the limits of each class interval, beginning at the bottom of the table with the lowest score and proceeding upward.
6. Count the number of observations that occur in each interval and enter that count as the frequency of the interval.

Question 8

Histogram

Answer 8

A graphical presentation of a grouped frequency distribution with frequencies represented as vertical bars (next to each other); it is appropriate for interval/ratio data.

Question 9

Frequency polygon

Answer 9

A graphical presentation of a grouped frequency distribution with frequencies represented as points ; it is appropriate for interval/ratio data.

Question 10

Relative frequency

Answer 10

Frequency divided by the size of the group, expressed as a proportion or percentage.

Question 11

Stem and leaf display

Answer 11

Optional way of presenting frequency distributions of interval/ratio data - not as widely used.

Question 12

What are the five steps for eyeball estimating a frequency distribution?

Answer 12

1. Axes - Draw and label the axes. X axis has the variable you are interested in. Vertical axis has the frequency (f).
2. Min and Max - Plot your estimates to the minimum and maximum of the variable.
3. Intermediate - Add intermediate values to the X-asis using round numbers.
4. Mode - Plot estimate(s) of the mode(s) of the frequency distribution.
5. Complete - Connect the parts of the sketch that you have just created, keeping the distribution smooth and continuous.

Question 13

Where is the mode on a frequency distribution?

Answer 13

The mode is the most frequently occurring value in a distribution; it lies directly below the highest point on a graphical frequency distribution.

Question 14

Unimodal distribution

Answer 14

A distribution that has one most frequently occurring value.

Question 15

Bimodal distribution

Answer 15

A distribution that has two most frequently occurring values.

Question 16

Symmetric distribution

Answer 16

A distribution whose left side is a mirror image of its right side.

Question 17

What type of distribution is usually found in nature?

Answer 17

Unimodal. Bimodal distributions only occur when there is a splitting of a population into relatively distinct parts.

Question 18

Positively skewed distribution

Answer 18

A distribution whose right tail is longer than its left tail.

Question 19

Negatively skewed distribution

Answer 19

A distribution whose left tail is longer than its right tail.

Question 20

Asymptotic

Answer 20

A distribution whose tail gradually approaches the x-axis but never actually touches it.

Question 21

Normal distribution

Answer 21

Normal distributions are unimodal, symmetric, and asymptotic which means they have a general bell shape.

Question 22

Bar graph

Answer 22

A graphical display of a frequency distribution where frequencies are represented as separated vertical bars. Used for nominal or ordinal data.

Question 23

What does the separation of the bars in a bar graph indicate?

Answer 23

Makes it clear that there are no intermediate values were measured and also that the order of the bars can be rearranged.

Question 24

How are the frequency distributions of ordinal data displayed?

Answer 24

Bar graphs, histograms or frequency polygons.

Question 25

What is the advantage using a bar graph for ordinal data?

Answer 25

It makes it clear that the intervals between points are not necessarily equal sized

Question 26

What is the disadvantage using a bar graph for ordinal data?

Answer 26

It implies that there are no intermediate values between the bars.

Question 27

What graphs should be be used for interval/ratio level data?

Answer 27

Histograms or frequency polygons.

Question 28

What graphs should be be used for nominal data?

Answer 28

Bar graphs.

Question 29

What graphs should be be used for ordinal data?

Answer 29

Bar graphs.