Question

A particular bulb has lifetimes of 1500 hours with a standard deviation of 6 hours. Find a range in which it can be guaranteed that 93.75% of the lifetimes of this brand of car lie.

(1489 and 1512)

(1482 and 1518)

(1476 and 1524)

(1470 and 1530)

Answer 1

Mean = 1500

Standard deviation = 6

Z value at 93.75% confidence interval = 1.534

$Mean\pm Z \frac{s}{\sqrt{n}}$

$1500\pm 1.534 \frac{6}{\sqrt{1}}$

$1500\pm 1.534 \times6$

(1489 and 1512)