Answer:
Hence total of 10 students are not able to complete the exam.
Step-by-step explanation:
Given:
Mean for completing exam =80 min
standard deviation =10 min.
To find:
how much student will not complete the exam?
Solution:
using the Z-table score we can calculate the required probability.
Z=(Required time -mean)/standard deviation.
A standard on an avg class contains:
60 students.
consider for 70 mins and then 90 mins (generally calculate ± standard deviation of mean)(80-10 and 80+10).
1)70 min
Z=(70-80)/10
Z=-1
Now corresponding p will be
P(z=-1)
=0.1587
therefore
Now for required 90 min will be
Z=(90-80)/10
=10/10
z=1
So corresponding value of p is
P(z<1)=0.8413
this means 0.8413 of 60 students are able to complete the exam.
0.8413*60
=50.47
which approximate 50 students,
total number =60
and total number student will able to complete =50
Total number of student will not complete =60-50
=10.
