Answer:
[tex]P(x \le 21) = 0.69146[/tex]
Step-by-step explanation:
The missing parameters are:
[tex]n = 64[/tex] --- population
[tex]\mu = 20[/tex] --- population mean
[tex]\sigma = 16[/tex] -- population standard deviation
Required
[tex]P(x \le 21)[/tex]
First, calculate the sample standard deviation
[tex]\sigma_x = \frac{\sigma}{\sqrt n}[/tex]
[tex]\sigma_x = \frac{16}{\sqrt {64}}[/tex]
[tex]\sigma_x = \frac{16}{8}[/tex]
[tex]\sigma_x = 2[/tex]
Next, calculate the sample mean [tex]\bar_x[/tex]
[tex]\bar x = \mu[/tex]
So:
[tex]\bar x = 20[/tex]
So, we have:
[tex]\sigma_x = 2[/tex]
[tex]\bar x = 20[/tex]
[tex]x = 21[/tex]
Calculate the z score
[tex]x = \frac{x - \mu}{\sigma}[/tex]
[tex]x = \frac{21 - 20}{2}[/tex]
[tex]x = \frac{1}{2}[/tex]
[tex]x = 0.50[/tex]
So, we have:
[tex]P(x \le 21) = P(z \le 0.50)[/tex]
From the z table
[tex]P(z \le 0.50) = 0.69146[/tex]
So:
[tex]P(x \le 21) = 0.69146[/tex]
