Statistics Flashcards
(19 cards)
Var(X) = …
E(X^(2)) - (E(X))^(2)
E(aX + b) = …
aE(X) + b
E(X + Y) = …
E(X) + E(Y)
Var(aX + b) =
a^(2) Var(X)
P(X = x) = …
( e^-λ )( λ^x ) / ( x! )
** In the formula book
In order for a Poisson distribution to be a suitable model, what must the events that occur be?
- Independently
- Singularly in Space or Time
- At a Constant, Average Rate
In order for a Binomial distribution to be a suitable model, what must the events that occur be?
- Cosistant probability each trial
- Fixed number of trials
- Independent
If ‘X ~ Po(λ)’ and ‘Y ~ Po(μ)’ are independent and within the same limitation :
X + Y = …
Po(λ + μ)
What is the value of Mean in a poisson distribution?
λ
What is the value of Mean in a binomial distribution?
np
What is the value of Varience in a binomial distribution?
np(1 - p)
What is the value of Varience in a poisson distribution?
λ
X^(2) = …
Σ ((O - E)^(2) / E)
When is a Poisson distribution a suitable approximation for binomial distribution?
- when n is large
- when p is small
How do you calculate the degrees of freedom (one-way table)?
df = Number of cells - number of constraints :
- subtract 1 if you know the number of trials.
- subtract 1 if you know the probability of success for a trial.
*This is after cells have been merged.
X^(2) = …
Σ ((O - E) / E)
How do you calculate the degrees of freedom (two-way table)?
df = (Row - 1)(column -1)
*This is after cells have been merged.
How do you calculate the expected frequency of a two-way table?
Expected Frequency = (Row Total)(Column Total) / (Grand Total)
What is the p-value?
TBC
