Normal test for statistically significant differences:

Step 1. Enter the input variables:

Xt = cases in test group =

Xc = cases in control group =

Nt = total in test group =

Nc = total in control group =

After entering above, press "calculate":

Step 2. Calculate risks to the test and control group:

Pt = risk to test group = Xt / Nt = /=

Pc = risk to control group = Xc / Nc = /=

Step 3. Calculate p and q variables:

p = [Xt + Xc] / [Nt + Nc] = [+] / [+] =

q = [ 1 - p ] = [1 - ] =

Step 4. Verify Normality (all four values given below must be > 5):

Nt*p = *=

Nt*q = *=

Nc*q = *=

Nc*p = *=

Step 5. Calculate the denominator of the equation:

(pq) (1/Nt + 1/Nc) =

[ (pq) (1/Nt + 1/Nc) ]1/2 =

Step 6. Calculate Z:

Z = [ Pt - Pc ] / [ (pq) (1/Nt + 1/Nc) ]1/2 =[-]/=

z-distribution

Step 7. Press "calculate" to determine p-value:

if z =

then the p-value =

Step 8. Remember assumptions for normal probability curve:

mean =

standard deviation =

right bound =