Answer:
The critical value of <em>z</em> for 99% confidence interval is 2.5760.
The 99% confidence interval for population mean number of lightning strike is (7.83 mn, 8.37 mn).
Step-by-step explanation:
Let <em>X</em> = number of lightning strikes on each day.
A random sample of <em>n</em> = 23 days is selected to observe the number of lightning strikes on each day.
The random variable <em>X</em> has a sample mean of,
and the population standard deviation,
.
The (1 - <em>α</em>)% confidence interval for population mean <em>μ</em> is:
![CI=\bar x\pm z_{\alpha/2}\frac{\sigma}{\sqrt{n}}](https://tex.z-dn.net/?f=CI%3D%5Cbar%20x%5Cpm%20z_%7B%5Calpha%2F2%7D%5Cfrac%7B%5Csigma%7D%7B%5Csqrt%7Bn%7D%7D)
Compute the critical value of <em>z</em> for 99% confidence interval is:
![z_{\alpha/2}=z_{0.01/2}=z_{0.005}=2.5760](https://tex.z-dn.net/?f=z_%7B%5Calpha%2F2%7D%3Dz_%7B0.01%2F2%7D%3Dz_%7B0.005%7D%3D2.5760)
*Use a <em>z</em>-table.
The critical value of <em>z</em> for 99% confidence interval is 2.5760.
Compute the 99% confidence interval for population mean number of lightning strike as follows:
![CI=\bar x\pm z_{\alpha/2}\frac{\sigma}{\sqrt{n}}\\=8.1\pm2.5760\times\frac{0.51}{\sqrt{23}}\\=8.1\pm0.2738\\=(7.8262, 8.3738)\\\approx(7.83, 8.37)](https://tex.z-dn.net/?f=CI%3D%5Cbar%20x%5Cpm%20z_%7B%5Calpha%2F2%7D%5Cfrac%7B%5Csigma%7D%7B%5Csqrt%7Bn%7D%7D%5C%5C%3D8.1%5Cpm2.5760%5Ctimes%5Cfrac%7B0.51%7D%7B%5Csqrt%7B23%7D%7D%5C%5C%3D8.1%5Cpm0.2738%5C%5C%3D%287.8262%2C%208.3738%29%5C%5C%5Capprox%287.83%2C%208.37%29)
Thus, the 99% confidence interval for population mean number of lightning strike is (7.83 mn, 8.37 mn).
The 99% confidence interval for population mean number of lightning strike implies that the true mean number of lightning strikes lies in the interval (7.83 mn, 8.37 mn) with 0.99 probability.