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2.4.8 Normal distribution as a model (A-level only)

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Question 26

The storage life of a specialized organic catalyst, CCC days, is modeled by a normal distribution with a mean of 45 days and a standard deviation of 8 days.

a.

Calculate the probability that a randomly selected batch of this catalyst lasts longer than 60.0 days.

[3]
b.

A 'warning threshold' is set at ddd days, such that the probability of a catalyst failing before this threshold is 0.08. Determine the value of ddd.

[3]
c.

A laboratory process requires the catalyst to remain effective for a further 5 days. Given that a specific batch of catalyst has already been stored for 60 days and is still effective, find the probability that it will last until the process is finished.

[3]

2.4.8 Normal distribution as a model (A-level only) Questions

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