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

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Question 36

A biologist is studying the weight of a rare species of caterpillar. The weights are known to be normally distributed with mean μ\muμ mg and standard deviation 1.2 mg1.2\text{ mg}1.2 mg. A random sample of 888 caterpillars is weighed, and their masses, in mg, are recorded as follows:

42.5,41.2,44.8,43.6,40.5,42.1,45.3,41.6 42.5, 41.2, 44.8, 43.6, 40.5, 42.1, 45.3, 41.6 42.5,41.2,44.8,43.6,40.5,42.1,45.3,41.6
a.

Calculate a 98%98\%98% confidence interval for μ\muμ, giving your limits correct to two decimal places.

[4]
b.

The biologist plans to collect 303030 further independent random samples, each consisting of 888 caterpillars. For each sample, a 98%98\%98% confidence interval for μ\muμ will be constructed.

Determine the probability that exactly 333 of these 303030 intervals will not contain μ\muμ.

[3]

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

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