Asked by Denzil
A true-false test consists of 10 items. What is the probability that Chris gets 80% or more for the test?
Answers
Answered by
Reiny
I assume you mean by just guessing.
he must get 8 right, or 9 right or 10 right
= C(10,8)(1/2)^8 (1/2)^2 + C(10,9)(1/2)^9(1/2) + C(10,10) (1/2)^10
= (1/2)^10 ( 45 + 9 + 1)
= 55(1/2)^10
= 55/1024
not good, better study
he must get 8 right, or 9 right or 10 right
= C(10,8)(1/2)^8 (1/2)^2 + C(10,9)(1/2)^9(1/2) + C(10,10) (1/2)^10
= (1/2)^10 ( 45 + 9 + 1)
= 55(1/2)^10
= 55/1024
not good, better study
Answered by
John
Hi,
Can you please show the steps for
C(10,8)(1/2)^8 (1/2)^2 + C(10,9)(1/2)^9(1/2) + C(10,10) (1/2)^10
to
= (1/2)^10 ( 45 + 9 + 1)
I am a bit confused.
Thank you in advance :)
Can you please show the steps for
C(10,8)(1/2)^8 (1/2)^2 + C(10,9)(1/2)^9(1/2) + C(10,10) (1/2)^10
to
= (1/2)^10 ( 45 + 9 + 1)
I am a bit confused.
Thank you in advance :)