From a population with mean 1056, a sample of 400 with sample mean 910 is taken. Then value of test statistic is (σ = 400):

-7.3

The correct answer is Option (3) → -7.3

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

$= \frac{910 - 1056}{400/\sqrt{400}}$

$= \frac{-146}{400/20}$

$= \frac{-146}{20}$

$= -7.3$

The value of test statistic is $-7.3$.