STATS ( HILD ) : CH 5 , 6 & 7 FORMULAS

 

z/t Scores:

"t" distribution for means "z" distribution for means "z" dist. for proportions

( n < 30 and s unknown ) ( n 30 , let s = s) (q = 1 p , np 5 & nq 5)

( df = n - 1 )

 

( 1 - a )% Confidence Intervals :

 

(df = n - 1 ) ( assume s = s ) ()

 

Sample Size :

( use if unknown )

 

 

Sample mean: Sample standard deviation:

 

 

For the Normal distribution: x z z x

 

 

-sampling one at a time (n=1): x = zs + m

 

 

-sampling n at a time

and finding the sample average, :

 

If np 5 and nq 5 , the Normal dist will approximate the Binomial dist. with : m = np and

 

or: