Unit 1 Flashcards
variable (def)
a characteristic that changes from one individual to another
collect data on variables from individuals
categorical variable (def)
takes on values that are category names or group lables
ex. age group, dominat hand, gender, grade level, zipcode
Quantitive variable
takes on numerical values for a measured or counted quanity
height, salt level in water, number of candies in a bag, age of building
relative frequency is…
propotional to the whole
what graphs are used for categorical data
- bar charts (aka bar graphs)
- pie charts
Bar charts NEVER ____
touch!
What are the cateigories in bar charts called (labels on the bottom)
bins
pie charts only display
relative frequencies
when comparing groups of diffrent sizes, do you use counts or propotions
proportions
what are the 2 types of quanitative variables
- Discrete
- Continous
Discrete vs. continous variable
Discrete: countable number of values
- ex. number of wins, number of skittles, amount of eruptions in a year
Continous: values that are theortically infinfite (measuring)
- ex. weight of frog, speed of a car
What graphs are for quanititve data
- dot plot
- steam and leaf plot
- histogram (most common)
- cumulative graph
histogram vs bar chart
histogram
- bars touch
- labels/numbers on line
- quantitive
Bar chart
- space between bars
- labels in the bins
- categorical
What does the slope mean in a cumulative graph
the steeper the slope, the more data in the range
no slope = no data
What things do you need to include when describing the distrubtion of a quantitative variable/graph
Shape - unimodial, bimodial, symmetical, skews
Outliers
Center - one value that summarizes data
Spread - how the data varies
The mean is easily influenced by…
outliers (non resistant)
best for symmetric data
Is the median resistant or non-resistant
resistant because it is not influenced by outliers
when the data is roughly symmetic, the mean and median are ____
the same (or pretty close together)
When the data is skewed left, the mean is ____ than the median
smaller
When the data is skewed right, the mean is ____ than the median
larger
Percentile
the value that P% of the data is less and or equal to it
- ex. If you take the SAT, and land in the 95% percentile, it means that 95% of the test takers got your score or lower
Main points in percentiles
- Q1: first quartile is the 25th percential or the median of the bottom half of data
- Median (overall): 50th percential
- Q3: 75th percentile or the median of the top half of data
How to transform the data
- add/subtract a value
- multipy all the values
how does adding/subtracting (transformations) effect the data
- measures of center
- measures of postion (percentiles/quartiles)
Measures of spead are not effected
how does multiplying (transformations) effect the data
effects all areas of statistics
- mean, median, IQR, etc.
elements of the 5 number summary
- min
- Q1
- median
- Q3
- Maximum
creates boxplot
