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

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Question 7

The lifespan of a certain type of industrial LED, measured in hours, is assumed to follow a normal distribution with mean μ\muμ and variance σ2\sigma^2σ2. Based on data from a single random sample of these LEDs, a 99%99\%99% confidence interval for μ\muμ was calculated to be:

(11484.84,12515.16) (11484.84, 12515.16) (11484.84,12515.16)

Using the data from this same sample:

a.

Determine a 95%95\%95% confidence interval for μ\muμ.

[4]
b.

Eight independent random samples are subsequently collected, and a 95%95\%95% confidence interval for μ\muμ is constructed for each of these eight samples.

Calculate the probability that exactly 7 of these 8 intervals will contain the true population mean μ\muμ.

[3]

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

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