Straighterline Introduction to Statistics exam questions and answers
Four steps in the process of statistics - Answer-1. Producing Data
2. Exploratory Data Analysis
3. Probability
4. Inference
Categorical variable - Answer-places individuals into one of several groups
Two types: nominal and ordinal
Quantitative Variable - Answer-represents a measurement or a count
Two types: Interval and ratio
Nominal Variable - Answer-categorical variables where there is no natural order among the categories
Ordinal variable - Answer-categorical variables where there is natural order among the categories
Interval Variable - Answer-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 - Answer-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 - Answer-nominal
What type of variable?:
socioeconomic status with categories low, med, high - Answer-Ordinal
What type of variable?:
Temperature - Answer-Interval
What type of variable?:
Income - Answer-Ratio
Visual display and numerical summary for a single categorical variable - Answer-pie chart or bar chart
and category percentages Visual display and numerical summary for a single quantitative variable - Answer-
histogram or stemplot and descriptive statistics
Visual display and numerical summary for C->C - Answer-Two way table and conditional percentages
Visual display and numerical summary for C->Q - Answer-Side by side box plots and descriptive statistics
Visual display and numerical summary for Q->Q - Answer-Scatterplot and correlation coefficient (r)
Standard Deviation Rule - Answer-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) - Answer-Middle 50% of the data
IQR= Q3-Q1
Finding an outlier using IQR - Answer-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 - Answer-1. upward slope
2. downward slope
Interpreting Scatterplots:
How to tell if a linear relationship is strong or weak - Answer-closer to -1 is a strong negative linear relationship
closer to +1 is a strong positive linear relationship
close to 0 is a weak linear relationship
Interpreting Scatterplots:
Linear regression - Answer-Finding the line that best fits the pattern of the linear relationship (the line that describes how the response variable linearly depends on the explanatory variable
Interpreting Scatterplots:
Least Squares Regression Line - Answer-Has the smallest sum of squared vertical deviations of the data points from the line.
Four steps in the process of statistics - Answer-1. Producing Data
2. Exploratory Data Analysis
3. Probability
4. Inference
Categorical variable - Answer-places individuals into one of several groups
Two types: nominal and ordinal
Quantitative Variable - Answer-represents a measurement or a count
Two types: Interval and ratio
Nominal Variable - Answer-categorical variables where there is no natural order among the categories
Ordinal variable - Answer-categorical variables where there is natural order among the categories
Interval Variable - Answer-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 - Answer-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 - Answer-nominal
What type of variable?:
socioeconomic status with categories low, med, high - Answer-Ordinal
What type of variable?:
Temperature - Answer-Interval
What type of variable?:
Income - Answer-Ratio
Visual display and numerical summary for a single categorical variable - Answer-pie chart or bar chart
and category percentages Visual display and numerical summary for a single quantitative variable - Answer-
histogram or stemplot and descriptive statistics
Visual display and numerical summary for C->C - Answer-Two way table and conditional percentages
Visual display and numerical summary for C->Q - Answer-Side by side box plots and descriptive statistics
Visual display and numerical summary for Q->Q - Answer-Scatterplot and correlation coefficient (r)
Standard Deviation Rule - Answer-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) - Answer-Middle 50% of the data
IQR= Q3-Q1
Finding an outlier using IQR - Answer-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 - Answer-1. upward slope
2. downward slope
Interpreting Scatterplots:
How to tell if a linear relationship is strong or weak - Answer-closer to -1 is a strong negative linear relationship
closer to +1 is a strong positive linear relationship
close to 0 is a weak linear relationship
Interpreting Scatterplots:
Linear regression - Answer-Finding the line that best fits the pattern of the linear relationship (the line that describes how the response variable linearly depends on the explanatory variable
Interpreting Scatterplots:
Least Squares Regression Line - Answer-Has the smallest sum of squared vertical deviations of the data points from the line.
