Answer:
a) M =82
Step-by-step explanation:
Let´s study this as a Normal distribution.
As we know in a normal distribution the z score is = (X-μ)/(sd/sqrt(n))
where
X = mean for the taken sample = What we want to know in this problem
μ = Total population mean =80
sd= standard deviation= 12
n = sample size=9
So in this case z=( X-80)/(12/sqr(9))= (X-80)/4
also we know that the effect size taken by the machine is 0.5, which is the same as the z-score
so...
0.5 = (X-80)/4 => 0.5*4 = X-80
2+80 = X
X = 82
What is 19 and 20 you didn’t put anything
