Straighterline Introduction to Statistics
Exam Study Guide.
Four steps in the process of statistics - Answers✔1. Producing Data
2. Exploratory Data Analysis
3. Probability
4. Inference
Categorical variable - Answers✔places individuals into one of several groups
Two types: nominal and ordinal
Quantitative Variable - Answers✔represents a measurement or a count
Two types: Interval and ratio
Nominal Variable - Answers✔categorical variables where there is no natural order among the
categories
Ordinal variable - Answers✔categorical variables where there is natural order among the
categories
Interval Variable - Answers✔a measurement or count for which it makes sense to talk about the
difference between values, but it does not make sense to talk about the ratio between values; 0
does not represent the absence of quanitity
Ratio Variable - Answers✔quantitative variables for which it makes sense to talk about the
difference between values AND the ratio between values; 0 represents the absence of quantity
What type of variable?:
eye color - Answers✔nominal
What type of variable?:
socioeconomic status with categories low, med, high - Answers✔Ordinal
What type of variable?:
Visual display and numerical summary for a single categorical variable - Answers✔pie chart or
bar chart
and category percentages
Visual display and numerical summary for a single quantitative variable - Answers✔histogram
or stemplot
and descriptive statistics
Visual display and numerical summary for C->C - Answers✔Two way table and conditional
percentages
Visual display and numerical summary for C->Q - Answers✔Side by side box plots and
descriptive statistics
Visual display and numerical summary for Q->Q - Answers✔Scatterplot and correlation
coefficient (r)
Standard Deviation Rule - Answers✔Approximately
68% of observations fall within 1 sd of the mean,
95% within 2 sd,
99.7% (or virtually all) within 3 sds
Interquartile Range (IQR) - Answers✔Middle 50% of the data
IQR= Q3-Q1
Finding an outlier using IQR - Answers✔An observation is considered a suspected outlier if it is:
less than Q1 - 1.5(IQR), or
more than Q3 + 1.5(IQR).
Interpreting scatterplots:
1. positive relationship displays as
2. negative relationship displays as - Answers✔1. upward slope
2. downward slope
Interpreting Scatterplots:
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