Homework Help: Statistics

Posted by Joy on Sunday, January 22, 2012 at 4:14pm.

Shown below are the data giving the length of life of lights in an underground tunnel.

9.0 months 7.0 months
8.2 months 8.3 months
7.8 months 8.1 months
7.5 months 7.6 months
9.1 months 7.4 months

I calculated the standard deviation to be about 0.679.
Estimate the probability that a random chosen light will last as long as 7 months after installation. Assume the data to be described by a normal distribution.

Can anyone help me with the process I would use to calculate the answer? Thanks!

Statistics - MathGuru, Sunday, January 22, 2012 at 7:31pm
Use z-scores. Find the mean. You have already calculated standard deviation.

Formula for z-scores is the following:
z = (x - mean)/sd

Use 7 for x. Calculate z-score. Determine the probability using a z-distribution table.
Statistics - Joy, Sunday, January 22, 2012 at 7:42pm
Thanks for the insight!

So I've calculated the z-score to be about -1.47, or about -1.5. Looking at a z-distribution table, I see on the left a column for z-scores and I see -1.5 there, but there are many values corresponding on the right?

Do you know how I know which one to use?
Statistics - Joy, Sunday, January 22, 2012 at 7:58pm
Never mind- I've figured it out, THANK YOU MathGuru!

Answer this Question

Related Questions

science - Shown below are the data giving the length of life of lights in an ...
Science can you help me - Praire dogs dig alot of underground tunnel systems ...
math - The number of streetlights in a town is growing linearly. Four months ago...
math - a tunnel under a river is 196.8 ft below the surface at its west point. ...
Statistics - The Centers for Disease Control and other organizations are ...
Statistics - the manufacturer of a certain brand of auto batteries claims the ...
Math - A tunnel under a river is 196.8 ft below the surface at its lower point. ...
English - what does this quote mean To write it, it took three months, to ...
Statistics - . A certain company makes 12-volt car batteries. After many years ...
stats - A manufacturer of automobile batteries claims that the distribution of ...

For Further Reading

First Name:
School Subject:
Answer: