Answer:
A) 0.0088
B) 0.2997
C) 5
Step-by-step explanation:
Given: Mean: Ч = 79 minutes
Standard deviation : б = 8 minutes
The formula for z score:
z= x-ц/σ
a) For x=60 minutes
z= 60-79/8 = -2.375
The p-value = P(z< -2.375) = 0.0087745 ≈ 0.0088
b) For x= 75 minutes
z= 75-79/8 = -0.5
The p-value = P(60 < x < 75) = P (-2.375 < z < -0.5)
= P(-0.5)-P(-2.375)= 0.3085 -0.0088 =0.2997
c) For x=90 minutes
z= 90-79/8 = 1.375
The p-value = P (z > 1.375)= 1-P(z < 1.375)
= 1-0.9154342 = 0.0845658
If the number of students in the class=60.
Then, the number of students will be unable to complete the exam in the alotted time = 0.0845658 x 60 = 5.073948 ≈ 5
