STT 215 EXAM 1 QUESTIONS WITH VERIFIED
ANSWERS
What is statistics? - ANSWER Collection or gathering of data
Displaying, analyzing, and summarizing data
Inferring information from data
Cases - ANSWER The objects described by a set of data. May be customers,
companies, subjects in a study, or other subjects (observations/individuals).
Label - ANSWER A special variable used in some data sets to distinguish
different cases.
Example: Patient A, Patient B, Patient C, etc.
Variable - ANSWER A characteristic that varies among individuals in a
population or in a sample (a subset of a population).
Example: age, height, blood pressure, ethnicity, leaf length, first language
Distribution - ANSWER Tells us what values the variable takes and how often
it takes these values.
Categorical variable - ANSWER Something that falls into one of several
categories. What can be counted is the count or proportion of individuals in
each category.
Example: blood type (A, B, AB, O), hair color, ethnicity
Quantitative (numerical) variable - ANSWER Something that can be counted
or measured for each individual and then added, subtracted, averaged, etc.
across individuals in the population.
Example: height, age, blood cholesterol level
Quantitative data: discrete versus continous - ANSWER Discrete if the
possible values are isolated points on the number line.
, Continuous if the set of possible values forms an entire interval on the number
line.
Ways to represent categorical data - ANSWER Frequency / Relative
Frequency distribution
Bar graph
Pie chart
Ways to represent numerical data - ANSWER Frequency distribution
Stemplot (stem-and-leaf plot)
Histogram
Ways to represent bivariate numerical data - ANSWER Scatter plot
Bar graph - ANSWER Each category is represented by a bar. The bar's height
shows the count (or sometimes the percentage) for that particular category.
Pie chart - ANSWER Peculiarity: the slices mist represent the parts of one
whole (1 or 100%). The size of a slice depends on what percent of the whole
this category represents.
Relative frequency - ANSWER (frequency) / (number of observations in the
data set)
Stemplot - ANSWER (Also called a stem-and-leaf plot) Each observation is
represented by a stem, consisting of all digits except the final one, which is the
leaf.
Work best for small numbers of observations that are all greater than 0.
Display the actual values of the observations.
How to make a stemplot - ANSWER Separate each observation into a stem
(consisting of all but the final (rightmost) digit), and a leaf (which is that
remaining final digit). Stems may have as many digits as needed, but each leaf
contains only a single digit.
Write the stems in a vertical column with the smallest value at the top, and draw
a vertical line at the right of this column.
Write each lead in the row of its stem, in increasing order out from the stem.
ANSWERS
What is statistics? - ANSWER Collection or gathering of data
Displaying, analyzing, and summarizing data
Inferring information from data
Cases - ANSWER The objects described by a set of data. May be customers,
companies, subjects in a study, or other subjects (observations/individuals).
Label - ANSWER A special variable used in some data sets to distinguish
different cases.
Example: Patient A, Patient B, Patient C, etc.
Variable - ANSWER A characteristic that varies among individuals in a
population or in a sample (a subset of a population).
Example: age, height, blood pressure, ethnicity, leaf length, first language
Distribution - ANSWER Tells us what values the variable takes and how often
it takes these values.
Categorical variable - ANSWER Something that falls into one of several
categories. What can be counted is the count or proportion of individuals in
each category.
Example: blood type (A, B, AB, O), hair color, ethnicity
Quantitative (numerical) variable - ANSWER Something that can be counted
or measured for each individual and then added, subtracted, averaged, etc.
across individuals in the population.
Example: height, age, blood cholesterol level
Quantitative data: discrete versus continous - ANSWER Discrete if the
possible values are isolated points on the number line.
, Continuous if the set of possible values forms an entire interval on the number
line.
Ways to represent categorical data - ANSWER Frequency / Relative
Frequency distribution
Bar graph
Pie chart
Ways to represent numerical data - ANSWER Frequency distribution
Stemplot (stem-and-leaf plot)
Histogram
Ways to represent bivariate numerical data - ANSWER Scatter plot
Bar graph - ANSWER Each category is represented by a bar. The bar's height
shows the count (or sometimes the percentage) for that particular category.
Pie chart - ANSWER Peculiarity: the slices mist represent the parts of one
whole (1 or 100%). The size of a slice depends on what percent of the whole
this category represents.
Relative frequency - ANSWER (frequency) / (number of observations in the
data set)
Stemplot - ANSWER (Also called a stem-and-leaf plot) Each observation is
represented by a stem, consisting of all digits except the final one, which is the
leaf.
Work best for small numbers of observations that are all greater than 0.
Display the actual values of the observations.
How to make a stemplot - ANSWER Separate each observation into a stem
(consisting of all but the final (rightmost) digit), and a leaf (which is that
remaining final digit). Stems may have as many digits as needed, but each leaf
contains only a single digit.
Write the stems in a vertical column with the smallest value at the top, and draw
a vertical line at the right of this column.
Write each lead in the row of its stem, in increasing order out from the stem.
