Question

What is the probability that sample mean is more than 12 million

Answer 1

P($\bar x >12)$

Assuming that the sample size, population mean and standard deviation are known,

Z=$\frac {\bar x - \mu} {\frac{ \sigma} {\sqrt n}}$

= $\frac {12 - \mu} {\frac{ \sigma} {\sqrt n}}$

Read the value of $P(z>\frac {12 - \mu} {\frac{ \sigma} {\sqrt n}} )$ from z-table.