Question

A&X Electrical makes a lamp. The Research department found that the life of the lamp is normally distributed with a mean of 5000 hours and a standard deviation of 450 hours.

1. Determine the z-score for a lamp that lasts 4000 hours.
z = 2.22 and the corresponding z score is .9865?

Answer 1

those are my answers i just want to make sure that someone can confirm that they are correct

Answer 2

zscore has to be negative, since the observation is less than mean

Answer 3

but the z is correct, right?

Answer 4

5000-4000/450

Answer 5

=2.22

Answer 6

it's

z = (x - mu)/sigma

NOT

z = (mu - x)/sigma

Answer 7

z = observation - mean / standard deviation

Answer 8

not the other way around

Answer 9

x=5000, mu=4000

Answer 10

the mean is 5000, so mu = 5000

Answer 11

= -2.2

Answer 12

z score = .0102?

Answer 13

the z-score is -2.2 (roughly)

Answer 14

I'm not sure what 0.0102 is referring to

Answer 15

if you look at the table of z scores

Answer 16

oh are you looking for the area under the curve to the left of z = -2.2 ?

Answer 17

am not sure. all i have to do is answer the quesiton that i posted. so if im just supposed to find the corresponding z score and -2.2 is it then no

Answer 18

I think they just want the z-score

Answer 19

so z = -2.222... (the 2's after the decimal repeat) or just z = -2.22 or something like that should do

Answer 20

ok thank you

Answer 21

you're welcome

Answer 22

if u want the area under curve :
http://www.wolframalpha.com/input/?i=zscore+-2.22

Answer 23

look at p-value

Answer 24

you should say :

z = 2.22 and the corresponding area is .9865?

Answer 25

or :

z = 2.22 and the corresponding probability is .9865?

Answer 26

I think they just want the z-score ganeshie8

Answer 27

okay thank you