Ch 3: Describing Data Using Distributions & Graphs Flashcards
What is a frequency distribution?
a way to take a disorganized set of scores and places them in order from highest to lowest and at the same time grouping everyone with the same score; can help researchers identify outliers; An arrangement of data showing how often different values occur in a dataset.
What is an outlier?
an observation of data that does not fit the rest of the data; sometimes called an extreme value; when you graph it, it will appear not to fit the pattern of the graph; An observation that falls significantly outside the general pattern of a distribution.
What are frequency tables?
it shows the frequencies of the various response categories; It also shows the relative frequencies, which are the proportion of responses in each
category
What is a grouped frequency table?
the ranges must all be of equal width, and there are usually between five and 15 of them; in which the first column lists ranges of values
and the second column lists the frequency of scores in each
range; can also be used for categorical variables, in which case the levels are category labels; they are often listed from the most frequent at the top to the least frequent at the bottom
What is a histogram?
a graphic version of a frequency distribution; It helps to display the shape of a distribution; The graph consists of bars of equal width drawn adjacent to each other and has both a horizontal axis and a vertical axis; The horizontal axis (x-axis) is labeled with what the data represents; The vertical axis is labeled either frequency or relative frequency (or percent frequency or probability); shows the distribution of the values including the highest, middle, and lowest value; A graphical representation of numerical data where bars represent frequency of data within intervals.
What are frequency polygons?
a graphical device for understanding the shapes of distributions; They serve the same purpose as histograms, but are especially helpful for comparing sets of data; also a good choice for displaying cumulative frequency distributions; A line graph showing the frequency distribution of a dataset.
What is a stem-and-leaf graph or stemplot?
comes from the field of exploratory data analysis; is a good choice when the data sets are small; A display showing each data value split into a “stem” (leading digits) and “leaf” (final digit).
What is are box plots?
useful for identifying outliers (extreme scores) and for comparing distributions; we put “whiskers” above and below each box to give additional information about the spread of data; Whiskers are vertical lines that end in a horizontal stroke; Whiskers are drawn from the upper and lower hinges to the upper and lower adjacent values; provide basic information about the distribution, examining data according to quartiles; By examining this you are able to identify more about the distribution; e good at portraying extreme values and are especially good at showing differences between distributions; A graphical display showing quartiles, median, and potential outliers of a dataset.
What two elements of frequency distribution must be present when using a table or a graph?
- the entire set of categories that make-up the original
distribution must be included - a record of the frequency, or number of individuals in each
category within the distribution must be included
What is a bar graph?
are often used to compare the means of different experimental conditions; can also be used to represent frequencies of different categories; may be appropriate for qualitative data (categorical variables) that use a nominal or
ordinal scale of measurement
What is the shape of distribution?
to learn how different shapes affect our numerical descriptors of data and distributions; the primary characteristic that we are concerned about is whether it is symmetrical or skewed; a symmetrical distribution can be cut down the center to form 2 mirror images; a skewed distribution is in which one of the two tails of the distribution is disproportionately longer than the other
What is Data Visualization?
The representation of data in graphical format to aid in understanding patterns and relationships.
What is Skewness?
The degree of asymmetry in a distribution; can be positive (right) or negative (left).
What is Class Interval?
The range of values grouped together in a frequency distribution.
What is a Normal Distribution?
A symmetrical, bell-shaped distribution of data.
