We use the formula: [tex]z = \frac{x-\mu}{\frac{\sigma}{ \sqrt{n}}} = \frac{x-\mu}{\frac{90}{\sqrt{100}}} = \frac{x-\mu}{9}[/tex]
a. [tex]z = \frac{5}{9} = 0.56[/tex], so we then find P(-0.56 < z < 0.56) from z-tables, and this is equivalent to 0.4246.
b.[tex]z = \frac{14}{9} = 1.56[/tex], so we find P(-1.56 < z < 1.56) from z-tables, and this value is equivalent to 0.8812.
