Descriptive Statistics Flashcards
describe/summarize the data a researcher has
descriptive statistics
helps a researcher understand the data that he has, while descriptive statistics help him explain to other people what is happening to his data
Exploratory data analysis (EDA)
The first thing to describe is the distribution of the data,
to show the kinds of numbers that we have.
describing data
- Different ways of Describing the Distribution
- is used to
present the pattern in the data.
- Frequency Table
- Charts (e.g., histograms, bar chart etc)
frequency distributions of nominal or ordinal data are customarily plotted using a ______
bar graph
____ drawn for each category, where the height of the
bars represent the frequency or number of members of
that category.
Bar
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.
histogram
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.
frequency polygon
Don’t draw a bar chart for ___
Continuous measures
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.
Frequency distribution
in grouping data
how wide should interval be?
When data are grouped
some information is lost
The wider the interval,
the more information is lost.
Constructing a frequency distribution of grouped scores
- Find the range of the scores.
- Determine the width of each class interval (i).
- List the limits of each class interval, placing the interval
containing the lowest score value at the bottom. - Tally the raw scores into the appropriate class intervals.
- Add the tallies for each interval to obtain the interval
frequency.
indicates the
proportion of the total number of scores in each interval.
Relative Frequency Distribution
indicates the
number of scores that fall below the upper limit of each
interval.
Cumulative Frequency Distribution
–indicates the
percentage of scores that fall below the upper limit of
each interval.
Cumulative Percentage Distribution
what is this symbol?
f/N
Relative Frequency
frequency of interval + frequencies of all class intervals below it.
Cumulative Frequency
what is this formula?
cum f / N x 100
cumulative percentage
_____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.
histogram
the normal distribution also known as the
Gaussian Distribution
_____ symmetrical and bell shaped. It
curves outwards at the top and then inwards nearer the
bottom, the tails getting thinner and thinner.
normal distribution
is the data form a perfect normal distribution?
never but as long as the distribution is close to a normal
distribution, it will not matter too much.