Boy Mow Chau's answer to Audrey's Junior College 1 H1 Maths Singapore question.
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answers for (i) & (ii) shown just for info.
for (iii), treat as linear combination of random variables. note that variances must always be ADDED together.
for (iv), it is a distribution within another distribution.
do check for calculation errors.
for (iii), treat as linear combination of random variables. note that variances must always be ADDED together.
for (iv), it is a distribution within another distribution.
do check for calculation errors.
Date Posted:
2 years ago
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I tried (iii), I also get the same answer as you. Could the answer be wrong?
The question gives the mean of male & female as 1.71 & 1.6 respectively, & ...
1.711-1.6 = 0.111
By symmetry of normal distribution ...
P(M-F<0.111) = 0.5
so P(M-F<0.2) must be greater than 0.5 (regardless of what is the variance).
Therefore, even if the answer 0.645 is not right, the answer of 0.323 is unreasonable.