The lengths of text messages are normally distributed with a population standard deviation of 4 characters and an unknown population mean. If a random sample of 24 text messages is taken and results in a sample mean of 27 characters, find a 99% confidence interval for the population mean. Round your answers to two decimal places. z0.10 z0.05 z0.04 z0.025 z0.01 z0.005 1.282 1.645 1.751 1.960 2.326 2.576 You may use a calculator or the common z-values above.

The 99% confidence interval for population mean μ is (24.90, 29.10).

Step-by-step explanation:

Let the random variable X is defined as the lengths of text messages.

It is provided that X follows a Normal distribution with an unknown population mean μ and standard deviation σ = 4.

The (1 - α) % confidence interval for population mean is:

Given:

Compute the 99% confidence interval for μ as follows:

Thus, the 99% confidence interval for population mean μ is (24.90, 29.10).

d. bc = 12 and ef = 16

step-by-step explanation:

we are given that δabc : δdef such that .

also, it is given that

so, from the options, we need that .

a.

b.

c.  

d.

as, we can see that only option d gives the same ratio as i.e. .

hence, the possible lengths are bc = 12 and ef = 16.

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step-by-step explanation: