stats 235

what is the difference between a study and an experiment

in an experiment a treatment is applied and the outcome is observed

in a study observations are made without the application of a treatment

two kinds of inferences and how can they be made

population inference: infer to a large population

• random sampling

causal inference: the change caused by a variable

• random assignment

what is a pareto chart

bar chart but ordered in decreasing frequency

what does skewness describe

where the tail of the data is

parameter vs statistic

parameter: summary measure calculated for population data

statistic: summary measure calculated for sample data

median vs mode vs mean

median: midpoint of data set (ranked in increasing or decreasing order)

→ RESISTANT to outliers

mode: the most frequent value (peak of histogram)

mean: the average

→ sensitive to outliers, usually on the tail end

what numbers are included in the 5 number summary

1. min

2. max

3. Q1

4. Q3

5. median

sample space (ex in a card pack)

set of all elementary outcomes

• Ace of Spades

• Seven of Hearts

• Jack of Clubs

complement vs intersection vs union

complement: the event does NOT happen

→ A^c

→ P(A^c) = 1 - P(A)

intersection: A and B happen together

→ A ∩ B

union: A, B OR both happen

→ A ∪ B

independent vs dependent vs disjoint

independent: can occur together but don’t affect each other

dependent: can occur together and affect each other (default)

disjoint: cannot occur together