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2.4.6 Probabilities using the normal distribution (A-level only)

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Question 47

In an agricultural study, the sugar concentration of a certain variety of sugar beets, SSS, is modelled by a normal distribution with mean μ=165\mu = 165μ=165 g/L and standard deviation σ=12\sigma = 12σ=12 g/L.

a.

Find an estimate for the proportion of beets that have a sugar concentration of less than 144 g/L.

[2]
b.

The study selects beets for a premium processing trial. All beets are tested, and the 12% with the highest sugar concentration qualify for the trial.

Find an estimate for the minimum sugar concentration required to qualify for the trial. Give your answer correct to 4 significant figures.

[3]
c.

Find an estimate for the median sugar concentration of the beets that qualify for the trial.

[3]
d.

Qualified beets undergo a secondary extraction process. The concentration achieved in the secondary process is independent of the first and follows the same normal distribution. Beets that achieve a concentration greater than 186 g/L in this secondary process are categorized as "Elite".

At the start of the study, a beet is selected at random.

Find the probability that this beet will be categorized as "Elite".

[3]

2.4.6 Probabilities using the normal distribution (A-level only) Questions

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