ZY's answer to QN's Junior College 1 H1 Maths Singapore question.
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Hi QN, pls note that the way you defined your variable is also incorrect. The binomial distribution is for the number of left-handed pupils, not the number of user-friendly chairs.
Date Posted:
4 years ago
Hi, would my probability be P(X>r) >= 0.95 if the qn asked for maximum number instead?
Hmm no. It is P(X<=r) because we want to meet the needs of the left-handed students, thus "no. of left-handed students <= no. of user-friendly chairs". Whether it is max or min doesn't affect the sign here.
The question be "What is the MAXIMUM number of user-friendly chairs to be AT MOST 95% certain that we can meet the needs of left-handed students". Perhaps u can try to see if u can come up with the correct eqn for this. Hint: we still want to meet the needs so the LHS doesn't change
Since the sign doesn’t matter for minimum and maximum in this case, I’m thinking it might still be P(X<=r) <= 0.95
P(X<=5) = 0.80421 <= 0.95
P(X<=6) = 0.91331 <= 0.95
P(X<=7) = 0.96786 >= 0.95
Therefore max number should be 6.
P(X<=5) = 0.80421 <= 0.95
P(X<=6) = 0.91331 <= 0.95
P(X<=7) = 0.96786 >= 0.95
Therefore max number should be 6.
Is it logical? Pls help me vet through :)
Yup that's right!
Thanks!! It was really helpful:)
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