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1. Anyone know how to do this? This is a question on my Uni practice exam but is of similar standard to S2...any ideas? Thanks

An article passes through three independent stages during its manufacture. The time taken, in minutes, in each stage is Normally distributed with mean and standard deviation given below.

Stage , Mean , Standard Deviation
Stage 1 , 23 , 3
Stage 2 , 32 , 4
Stage 3 , 13 , 1

What is the probability that the total production time for an article exceeds 65 minutes
2. (Original post by markh1234)
Anyone know how to do this? This is a question on my Uni practice exam but is of similar standard to S2...any ideas? Thanks

An article passes through three independent stages during its manufacture. The time taken, in minutes, in each stage is Normally distributed with mean and standard deviation given below.

Stage , Mean , Standard Deviation
Stage 1 , 23 , 3
Stage 2 , 32 , 4
Stage 3 , 13 , 1

What is the probability that the total production time for an article exceeds 65 minutes
the combined time will also be normally distributed
with mean 23 + 32 + 13
and variance 32 + 42 + 12

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