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 ³ 30 , let s = s) (q = 1 – p , np ³ 5 & nq ³5)

( 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 = z×s + m

-sampling “n” at a time

and finding the sample average, :

If np ³ 5 and nq ³ 5 , the Normal dist will approximate the Binomial dist. with : m = n×p and

or: