Descriptive Statistics

Question 1

describe/summarize the data a researcher has

Answer 1

descriptive statistics

Question 2

helps a researcher understand the data that he has, while descriptive statistics help him explain to other people what is happening to his data

Answer 2

Exploratory data analysis (EDA)

Question 3

The first thing to describe is the distribution of the data,
to show the kinds of numbers that we have.

Answer 3

describing data

Question 4

• Different ways of Describing the Distribution
• is used to
  present the pattern in the data.

Answer 4

• Frequency Table
• Charts (e.g., histograms, bar chart etc)

Question 5

frequency distributions of nominal or ordinal data are customarily plotted using a ______

Answer 5

bar graph

Question 6

____ drawn for each category, where the height of the
bars represent the frequency or number of members of
that category.

Answer 6

Bar

Question 7

used to represent frequency distributions
composed of interval or ratio data. Bar is drawn for each
class interval.

• Class intervals are plotted on the horizontal axis such
  that each class bar begins and terminates at the real
  limits of the interval.

Answer 7

histogram

Question 8

also used to represent interval or
ratio data.

Instead of using bars, a point is plotted over the midpoint
of each interval at a height corresponding to the
frequency of the interval. Points are joined by a straight
line.

Answer 8

frequency polygon

Question 9

Don’t draw a bar chart for ___

Answer 9

Continuous measures

Question 10

presents the score values and
their frequency of occurrence.

When presented in a table, the score values are listed in
rank order, with the lowest score value usually at the
bottom of the table.

Answer 10

Frequency distribution

Question 11

in grouping data

Answer 11

how wide should interval be?

Question 12

When data are grouped

Answer 12

some information is lost

Question 13

The wider the interval,

Answer 13

the more information is lost.

Question 14

Constructing a frequency distribution of grouped scores

Answer 14

1. Find the range of the scores.
2. Determine the width of each class interval (i).
3. List the limits of each class interval, placing the interval
   containing the lowest score value at the bottom.
4. Tally the raw scores into the appropriate class intervals.
5. Add the tallies for each interval to obtain the interval
   frequency.

Question 15

indicates the
proportion of the total number of scores in each interval.

Answer 15

Relative Frequency Distribution

Question 16

indicates the
number of scores that fall below the upper limit of each
interval.

Answer 16

Cumulative Frequency Distribution

Question 16

–indicates the
percentage of scores that fall below the upper limit of
each interval.

Answer 16

Cumulative Percentage Distribution

Question 17

what is this symbol?

f/N

Answer 17

Relative Frequency

Question 18

frequency of interval + frequencies of all class intervals below it.

Answer 18

Cumulative Frequency

Question 19

what is this formula?

cum f / N x 100

Answer 19

cumulative percentage

Question 20

_____are very important in data analysis, because
they allow us to examine the shape of the distribution of
a variable.

The shape is a pattern that forms when a _____ is
plotted and is known as the distribution.

Answer 20

histogram

Question 21

the normal distribution also known as the

Answer 21

Gaussian Distribution

Question 22

_____ symmetrical and bell shaped. It
curves outwards at the top and then inwards nearer the
bottom, the tails getting thinner and thinner.

Answer 22

normal distribution

Question 23

is the data form a perfect normal distribution?

Answer 23

never but as long as the distribution is close to a normal
distribution, it will not matter too much.

Question 24

A very ___ of naturally occurring variables are
normally distributed.

A _____ of statistical tests make the assumption
that the data form a normal distribution.

Answer 24

large number

Question 25

don’t refer to the Normal Distribution as either of the
following;

Answer 25

usual, regular, standard, or even distribution.

Question 25

Wrong Shape

Distributions can be of wrong shape for two reasons.

First, because it is not symmetrical –

Second, because it is not the characteristic bell shape

Answer 25

• SKEW
• KURTOSIS

Question 26

A non-symmetrical distribution is said to be _____.

Answer 26

SKEW

Question 26

the curve rises rapidly and then drops off
slowly.

Answer 26

positive skew

Question 26

the curve rises slowly and then
decreases rapidly.

Answer 26

negative skew

Question 27

Skewness has some serious implications for some types
of data analysis.

Skew often happens because of ____ or _____

Answer 27

floor effect or ceiling effect

Question 28

occurs when only few of the subjects are
strong enough to get off the floor.

Answer 28

floor effect

Question 29

causes negative skew and are much less
common in Psychology.

sometimes occur most commonly when we
are trying to ask questions to measure the range of some
variable, and the questions are all too easy, or too low
down the scale.

Answer 29

ceiling effect

Question 29

Much trickier than Skew but is usually less of a problem.

Occurs when there are either too many people at the
extremes of the scale, or not enough people at the
extremes.

Answer 29

kurtosis

Question 30

when there are insufficient people in
the tail (ends) of the scores to make the distribution
normal.

Answer 30

positive kurtosis

Question 31

when there are too many people,
too far away, in the tails of the distribution.

Answer 31

negative kurtosis

Question 32

_____ is just a “posh” way of saying average.

In some way refers to the most central value of a data
set with different interpretations of the sense of
“central”.

Loosely known as the average. In statistical description,
though, we have to be more precise about just what sort
of average we mean.

Answer 32

central tendency

Question 32

Small number of data points that lie outside the
distribution when the distribution is approximately
normal.

Usually easily spotted in histograms.

______ are easy to spot but deciding what to do with
them can be much trickier.

Answer 32

outliers

Question 33

The mean is very sensitive to _____

Answer 33

extreme scores

Question 33

Called the arithmetic mean.

Calculated by adding up all the scores and dividing by the
number of individual scores.

Equation: (?) = ∑x / N

Answer 33

Mean

Question 33

Under most circumstances, of the measures used for
central tendency, the mean is least subject to ______

Answer 33

sampling variation

Question 33

For statistics to be correct, we need to make some _____

Answer 33

assumptions

Question 34

The sum of the squared deviations of all the scores
about their mean is a ______

Answer 34

minimum

Question 35

the _____ is equal to the sum of the mean of each
group times the number of scores in the group, divided
by the sum of the number of scores in each group.

Answer 35

overall mean

Question 36

Second most common measure of central tendency.

It is the middle score in a set of scores.

Used when the mean is not valid, which might be
because the data are not symmetrically or normally
distributed, or because the data are measured in an
ordinal level.

Answer 36

Median

Question 37

The median is _____ than the mean to extreme
scores.

Answer 37

less sensitive

Question 38

The most frequent score in the distribution or the most
common observation among a group of scores.

Best measure of central tendency for CATEGORICAL data
(although it is not even very useful for that)

Rarely used in research.

Answer 38

mode

Question 39

In a frequency distribution it is very easy to see because
it is the _______ of the distribution.

The problem with it is it does not tell us very much.

Answer 39

highest point

Question 40

The _____ is the simplest measure of dispersion.

It is the distance between the highest score and the
lowest score.

It can be expressed as a single number, or sometimes it is
expressed as the highest and lowest scores.

Answer 40

range

Question 41

To find the range we find the lowest value (2) and the
highest value (17). Sometimes the range is expressed as
a single figure, calculated as:

Answer 41

Range = Highest Value – Lowest Value

Question 42

Used with ordinal data or with non-normal distributions.

If median is used as a measure of central tendency, the ___ is probably used as a measure of dispersion.

It is the distance between the upper and lower quartiles.

Answer 42

inter-quartile-range

Question 43

There are ____ quartiles in a variable – they are the____ values that divide the variable into four groups.

Answer 43

three

Question 44

The ____ quartile happens one quarter of the way up the
data, which is also the 25th centile.

Answer 44

1st quartile

Question 45

The _____ quartile is the half-way point, which is the
median, and is also the 50th centile.

Answer 45

2nd quartile

Question 46

The ____ quartile is the three-quarter-way point or the 75th
centile.

Answer 46

third quartile

Question 47

symbol

s

Answer 47

sample standard deviation

Question 47

______ is like the mean, in that it
takes all of the values in the dataset into account when
it is calculated.

It is also like the mean in that it needs to make some
assumptions about the shape of the distribution.

To calculate the _____, we must assume that we have a
normal distribution.

Answer 47

Standard Deviation

Question 48

symbol

σ

Answer 48

population standard deviation

Question 49

the _____ of a set of scores is just the square of the standard deviation

Answer 49

variance

Question 50

the variance is not used much in descriptive statistics because it gives us squared units of measurement. however, it is used quite frequently in ___________

Answer 50

inferential statistics

Question 51

1. the SD gives us a measure of dispersion relative to the mean
2. the SD is sensitive to each score in the distribution
3. like the mean, the SD is stable with regard to sampling fluctuations

Answer 51

properties of the standard deviation

Question 52

population standard deviation

Answer 52

boxplot or box and whisker plot