science
posted by Joy .
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!

science 
PsyDAG
I assume that you have calculated the mean to find the SD.
Z = (scoremean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to the Z score.
Respond to this Question
Similar Questions

human growth and development
According to the Bayley Scales of Infant Development,most children who are ? 
math
John's account of 98.50 has been delinquent for 3 months. After 90 days office charges a 2% service charge, compounded monthly that is added to future bills. What would be the amount owed after 9 months? 
Statistics
. A certain company makes 12volt car batteries. After many years of product testing, the company knows that the average life of a battery is normally distributed, with a mean of 45 months and a standard deviation of 7 months. If the … 
Statistics
A certain company makes 12volt car batteries. After many years of product testing, the company knows that the average life of a battery is normally distributed, with a mean of 45 months and a standard deviation of 7 months. If the … 
math
A person takes out a monthly installment loan of $2000 with an annual percentage rate of 13.0% if the person can afford no more than $70 per month, then which of the following terms are feasible? 
Statistics
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 … 
Financial Mathematics
The Z Corporation needs $180,000 in 60 months. If they deposit $2,000 per month for the first 20 months, $2,500 for the next 20 months, and $2,000 + R for the last 20 months, what is R if they can invest at 7%(12)? 
Algebra
On her birthday today, Ali's age in months is twice her age in years 60 years from now. How old is Ali now, in months? 
Math
Caroline saves $45 in 4 months. At this rate, how long will it take her to save $180? 
Health, Fitness, and Nutrition
This is the length of time it takes for a fetus to become fully developed. A) 24 months B) 9 months C) 12 months D) 2 months