Math

f the life, in months, of a certain type of car battery is normally distributed with a mean of 88months and a standard deviation of 9 months, what should be the guarantee period if the companywants less than 5% of the batteries to fail while under warranty?

Answers:
A)Less than 16.13 monthsB)Less than 73.15 monthsC)Less than 64.78 monthsD)Less than 102.85 months

The Correct one is B, but I don't know how to get it. Can someone show me a step by step solution please.

  1. 👍 0
  2. 👎 0
  3. 👁 59
asked by Bailey
  1. this like your 1st question except you're going the other way with the z-score table

    they give you the population percentage and want the z-score
    ... the table shows -1.645
    ... multiply by 9 to find the number of months less than 88

    1. 👍 0
    2. 👎 0
    posted by scott
  2. same webpage I gave you before:
    https://www.jiskha.com/display.cgi?id=1524703735
    click on : value from an area
    enter:
    area = .05
    mean = 88
    SD = 9
    click on "below" to get 73.193

    1. 👍 0
    2. 👎 0
    posted by Reiny
  3. I meant to give you this page:
    http://davidmlane.com/normal.html

    1. 👍 0
    2. 👎 0
    posted by Reiny
  4. Thank you both!

    1. 👍 0
    2. 👎 0
    posted by Bailey

Respond to this Question

First Name

Your Response

Similar Questions

  1. Statistics

    . A certain company makes 12-volt 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

    asked by Jacob on June 20, 2010
  2. Statistics

    A certain company makes 12-volt 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

    asked by Toni on September 29, 2010
  3. stats

    A manufacturer of automobile batteries claims that the distribution of battery life is 54 months with a standard deviation of 6 months. We take a random sample of 50 batteries. a. Find the probability that their mean life is less

    asked by michelle on July 31, 2011
  4. Math

    LongLast Inc. produces car batteries. The mean life of these batteries is 60 months. The distribution of the battery life closely follows the normal probability distribution with a standard deviation of 8 months. As part of its

    asked by Mark on April 25, 2014
  5. math

    the battery lifetime is normally distributed for large samples with a standard deviation of 70 days. if 16% of the batteries have a lifetime of 850 or higher, what is the average battery life?

    asked by courtney on January 16, 2017
  6. economics

    An electronics company advertises that the battery life of its new smart phone with normal usage averages 72 hours. The company says this is one of the desirable characteristics of the phone which makes the phone a better choice

    asked by miguel on September 8, 2014
  7. economics 7

    An electronics company advertises that the battery life of its new smart phone with normal usage averages 72 hours. The company says this is one of the desirable characteristics of the phone which makes the phone a better choice

    asked by Mia on September 7, 2014
  8. economics (7)

    An electronics company advertises that the battery life of its new smart phone with normal usage averages 72 hours. The company says this is one of the desirable characteristics of the phone which makes the phone a better choice

    asked by miguel on September 8, 2014
  9. statistics

    The life span of the battery pack is known to be Normally distributed with a mean of 250 hours and a standard deviation of 20 hours. How to find the percentage of the battery packs lasting more than 250 hrs.

    asked by noe on May 6, 2012
  10. 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

    asked by Joy on January 22, 2012

More Similar Questions