Unit 1(B) Flashcards
What is the median
Middle number of a set of numbers arranged in numerical order
What is the mean
Found by summing all terms then dividing by number of terms
Characteristic of median
Resistant to extreme values and outliers.
Which type of statisic is median used in
Descriptive
What type of statistic is mean used in
Inferrential
4 ways to describe variability and dispersion
Range
Interquartile range
Variance
Standard deviation
What is the range
Diff between largest and smallest value
What is the interquartile range
Diff between largest and smallest value after removing the largest and smallest quarters.
How much % of data is the IQR
How to calc
Middle 50%
Q3 - Q1 = 75th percentile - 25th percentile
What is the variance
Averaging the squared diff of all the values from the mean
What is the standard deviation
Square root of variance
Adv and disadv of range
Adv:
Quick
Easy to calc
Disadv:
Completely depends on 2 extreme values
Ignores all middle values
Adv and disadv of IQR
Adv:
Removes influence of extreme values
Helps catch outliers
How to catch outliers via IQR
If a value is 1.5 * IQR less than Q1 or 1.5 * IQE more than Q3 it is an outlier.
What does standard deviation give a measure of
measure of the spread of the x-values around the sample mean
3 ways to designate positions
Simple ranking
Percentile
Z score
What is simple ranking
which involves arranging the elements in some order and noting where in that order a particular value falls
What is Percentile ranking
which indicates what percentage of all values fall below the value under consideration
What is Z score and what does it do
how many standard deviations a particular value varies from the mean.
Normalizes data
When is percentile used (related to the population)
When population size is unknown or irrelevant.
Formula for Z score
(X-avg)/sd
Avg and s/d of Z score
0, 1
Empirical rule - data distribution compared to SD
What distribution shape can it be applied to
68% of data lies within 1 sd
95% of data lies within 2 sd
99.7% of data within 3 sd of the mean
Symmetric bell shaped data
Central tendency of a symmetrical/normal curve
Center = mean, median and mode
Central tendency of skewed left
Mode < median < mean
Central tendency of skewed right
Mode > median > mean
What all does a boxplot display
Shows the smallest and largest value. The median, Q1 and Q3.
What values are sensitive to outliers vs resistant
Median and IQR resistant
Mean, range, variance, s/d are sensitive
What graph is used to compare distributions
back to back stemplot
How does changing units/multiplying values by a constant effect all values.
Mean, median, range, s/d remain constant.
