Stats

posted by .

A new extended-life light bulb has an average service life of 750 hours, with a standard deviation of 50 hours. If the service life of these light bulbs approximates a normal distribution, about what percent of the distribution will be between 600 and 900 hours?
a. 95 percent
` b. 68 percent
c. 34 percent
d. 99.7 percent
e. cannot be determined from the information given.

also please explain how you get the answer...

  • Stats -

    Z = (score-mean)/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 scores.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. statistics, help

    Can someone help me which way can I approach this problem. A hint of a formula or anything would be helpful... Life of Light Bulbs A certain type of light bulb has an average life of 500 hours, with a standard deviation of 100 hours. …
  2. stat

    A company installs 5000 light bulbs, each with an average life of 500 hours, standard deviation of 100 hours, and distribution approximated by a normal curve. Find the percentage of bulbs that can be expected to last the period of …
  3. statitics

    a light bulb manufacture gaurentees that the mean life of a certain type of bulb is at least 875 hours. A random sample of 40 light bulbs has a mean life of 863 hours with a standard deviation of 50. a=0.04
  4. Math

    A consumer buys n light bulbs, each of which has a lifetime that has a mean of 800 hours, a standard deviation of 100 hours, and a normal distribution. A light bulb is replaced by another as soon as it burns out. Assuming independence …
  5. Math

    A consumer buys n light bulbs, each of which has a lifetime that has a mean of 800 hours, a standard deviation of 100 hours, and a normal distribution. A light bulb is replaced by another as soon as it burns out. Assuming independence …
  6. statistics

    A new extended-life light bulb has an average service life of 750 hours, with a standard deviation of 50 hours. If the service life of these light bulbs approximates a normal distribution, about what percent of the distribution will …
  7. math

    1) A light bulb producing company states that its lights will last an average of 1200 hours with a standard deviation of 200 hours. A sample of 100 light bulbs from the company were tested and the researcher found that the average …
  8. statisitics

    A company installs 5000 light bulbs, each with an average life of 500 hours, standard deviation of 100 hours, and distribution approximated by a normal curve. How many bulbs should have a life expectancy between 400 and 600 hours?
  9. maths

    the life span of an electric bulb is normally distribution with mean 5500 light hours and standard deviation of 1200 light hours . what is the probability that a randomly selected bulb which lasts more than 6000 light hours?
  10. Statistics

    Construct a 99% confidence interval for life expectancy of a new GE light bulb. 64 bulbs are randomly selected and a mean of 750 hours and a standard deviation of 20 hours is found. Assume the distribution of life expectancy is normally …

More Similar Questions