รบกวนช่วยตรวจคำตอบให้หน่อยค่ะ ถ้าตอบผิดรบกวนชี้แนะด้วยค่ะ
1.z is the standard normal distribution or normal (mean=0,sd=1). find value p(-1.58<z<2.24)
ตอบ 0.9304

2. public school that score in the top 20% are labeled excellent. schools in the bottom 25% are designated as failing. previous data suggests that scores are approximately normal with a mean of 75 and standard deviation of 5.
What is the score cut-off required for schools to be labeled excellent?
ตอบ
ค่า z ที่ 0.2 = 0.0793
0.0793=(x-m)/sd
0.0793= (x-75)/5
(0.0793*5)+75 =x
75.3965=x