Before proceeding to the question, bear in english is not my native language and therefore technical terms may be wrong.
So, I'm trying to solve the old exam question, and I have different results from the solutions the teachers gave (they only gave the final answer).
There are 2 melon stores. The melon weights follow a normal distribution.
- Store A -> μ = 2.1Kg, σ = 0.7Kg;
- Store B -> μ = 2.5Kg, σ = 0.2Kg;
They ask, if I pick 3 melons, which store should I choose to maximize the probability of their total weight be above 8Kg.
So, I solved like (for store A) Z = (8 - (2.1 * 3)) / (0.7 * 3) = 0.8095 and then went on the table I found 0.2090 as the answer (did the same thing for store B, 0.2033).
I should choose store A as it has a bigger probability.
BUT, the problem is, the teachers solutions are 0.0804 and 0.0745.
What am I doing wrong? Is it the multiplication of the μ and σ?
I have not study Statistics for 4 years (working), so i'm a little rusty on the subject. A little help would be appreciated.
Thank you very much.