Statistics final wgu academy exam questions
and answers
Categorical variables that there is no natural order among the categories
nominal variables
Categorical variables where there is natural order among the categories (low-high)
ordinal variable
A measurement which makes sense to talk about the difference between values but not the ratio
between values
interval
Quantitive variables where is makes sense to talk about the difference in ratios. (Income, weight)
ratio
Value 0 means the absence of quantity (income $0)
In ratios:
Tells us what values the variables take and how often they take those values
Distribution of a Variable
Vale 0 does not mean the absence of value (temp = 0F)
In intervals:
Emphasize how the different categories relate to the whole
Pie charts
Emphasize how the different categories compare with each other
Bar charts
Breaking the range of values into intervals and count how many observations fall into interval.
Histogram
Graphical display of quantitive data. Data is spread into "stem" and "leaf". It retains the data and
sorts.
Stemplot(stem and leaf plot)
Graphically represents the distribution of a quantitive variable. Visually displays the five number
summary and the observations classified as a suspected outlier.
Boxplot
Mode, mean, and median.
Measures of Center
, The most commonly occurring value. Can be unimodal or bimodal
Mode
The average of a set of observations.
The sum of observations divided by the number of observations. (x bar)
Mean
The midpoint of the distribution. (M)
Median
Range, inter quartile range (IQR), standard deviation
Measures of soread
-order the data smallest to largest
-if the number(n) of observations is odd (n+1)/2nd spot
-if the number(n) of observations is even we have two n/2 = spot & n/2 + 1 = spot
How to find the median
Mean
Measure of center that is sensitive to outliers
Median
Measure of center that is not sensitive to outliers
Mean and median will be approximately equal
Symmetric distributions
Mean will be greater than the median
skewed right
Mean will be less than the median
skewed left
The exact distance between the smallest data point and the largest. The most intuitive measure of
variability.
range
Measures the variability of a distribution by giving us the range covered by the MIDDLE 50% of the
data.
- Step 1: Arrange the data in increasing order, and find the median
- Step 2: Find the median of the lower 50% of the data = 1st quartile (Q1)
- Step 3: Repeat this again for the top 50% of the data = 3rd quartile (Q3)
- Step 4: The middle 50% of the data falls between Q1 and Q3. Therefore: IQR = Q3 - Q1
and answers
Categorical variables that there is no natural order among the categories
nominal variables
Categorical variables where there is natural order among the categories (low-high)
ordinal variable
A measurement which makes sense to talk about the difference between values but not the ratio
between values
interval
Quantitive variables where is makes sense to talk about the difference in ratios. (Income, weight)
ratio
Value 0 means the absence of quantity (income $0)
In ratios:
Tells us what values the variables take and how often they take those values
Distribution of a Variable
Vale 0 does not mean the absence of value (temp = 0F)
In intervals:
Emphasize how the different categories relate to the whole
Pie charts
Emphasize how the different categories compare with each other
Bar charts
Breaking the range of values into intervals and count how many observations fall into interval.
Histogram
Graphical display of quantitive data. Data is spread into "stem" and "leaf". It retains the data and
sorts.
Stemplot(stem and leaf plot)
Graphically represents the distribution of a quantitive variable. Visually displays the five number
summary and the observations classified as a suspected outlier.
Boxplot
Mode, mean, and median.
Measures of Center
, The most commonly occurring value. Can be unimodal or bimodal
Mode
The average of a set of observations.
The sum of observations divided by the number of observations. (x bar)
Mean
The midpoint of the distribution. (M)
Median
Range, inter quartile range (IQR), standard deviation
Measures of soread
-order the data smallest to largest
-if the number(n) of observations is odd (n+1)/2nd spot
-if the number(n) of observations is even we have two n/2 = spot & n/2 + 1 = spot
How to find the median
Mean
Measure of center that is sensitive to outliers
Median
Measure of center that is not sensitive to outliers
Mean and median will be approximately equal
Symmetric distributions
Mean will be greater than the median
skewed right
Mean will be less than the median
skewed left
The exact distance between the smallest data point and the largest. The most intuitive measure of
variability.
range
Measures the variability of a distribution by giving us the range covered by the MIDDLE 50% of the
data.
- Step 1: Arrange the data in increasing order, and find the median
- Step 2: Find the median of the lower 50% of the data = 1st quartile (Q1)
- Step 3: Repeat this again for the top 50% of the data = 3rd quartile (Q3)
- Step 4: The middle 50% of the data falls between Q1 and Q3. Therefore: IQR = Q3 - Q1
