Saturday

September 20, 2014

September 20, 2014

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

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 7:31pmUse 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 7:42pmThanks 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 7:58pmNever 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 ...

Statistics - . A certain company makes 12-volt car batteries. After many years ...

math - A person takes out a monthly installment loan of $2000 with an annual ...

Statistics - A certain company makes 12-volt car batteries. After many years of ...

math - John's account of 98.50 has been delinquent for 3 months. After 90 days ...

human growth and development - According to the Bayley Scales of Infant ...

stats - 2. The average age of a child in kindergarten is 66 months. The standard...

math - Mrs. Diaz wishes to save at least $1500 in 12 months. If she save $300 ...

stats - A manufacturer of automobile batteries claims that the distribution of ...

math - Solve. The total sales made by a salesperson were $25,000 after 3, months...