Statistical Formula Sheet

Lab Test #1 Cheat Sheet

Binomial:

* Discrete distribution

* Sequence of n independent events

Only one of two possible outcomes

Cumulative =BINOMDIST(number of objects, number of trials,probability,1)

Eg.

Poisson distribution

* Discrete distribution

* Succession of events happening over some interval

* Events occur individually

* Their timing or spacing is unpredictable

* Events are independent

Cumulative =POISSON(number of trials, avg rate/hour,1)

E.g.

Exponential Distribution

* Continuous distribution

* Randomly occurring events occurring over some continuous interval

* Describes length of an interval between events in situations where there is a succession of independent, random events

Cumulative =EXPONDIST(interval (hours), avg rate/hour,1)

Eg.

Excel Functions:

1. NORMDIST gives the probability that a number falls at or below a given value of a normal distribution

2. NORMINV is the inverse of the NORMDIST function. It calculates the x variable given a probability

3. NORMSDIST translates the number of standard deviations (z) into cumulative probabilities

4. NORMSINV is the inverse of NORMSDIST function. Given the probability that a variable is within a certain distance of the mean, it finds the z value

Cumulative =NORMDIST(<length, mean, stdev, 1)

Degrees of Freedom: a mathematical restriction that we need to put in place when we calculate an estimate one statistic from an estimate of another

* Each item being estimated costs one degree of freedom. The remaining degrees of freedom are used to estimate variability

DoF = n-1-(#of estimated parameters)

Chi-square test: 1. Find the expected frequencies, 2. Find the errors for each interval, 3 add up the error, the sum is X2 calc-6.3463143992, 4. Find the degrees of freedom, 5. Find X2 using =0.05 significance level

If X2 calc < X2 crit., then not too much errors, observed follows distribution

Chi-square...