Question

The life of light bulbs is distributed normally. The variance of the lifetime is 625 and the mean lifetime of a bulb is 570 hours. Find the probability of a bulb lasting for at least 599 hours. Round your answer to four decimal places.

Answer #1

Variance = 625

Standard deviation = Sqrt(625) = 25

**z score normal distibution formula:**

**z = (x - μ) / σ**

**z = (599-570)/25 = 1.16**

**P(Z < 1.16) = 0.8770**

The probability of a bulb lasting for at least 599 hours is 0.8770

The life of light bulbs is distributed normally. The variance of
the lifetime is 400 and the mean lifetime of a bulb is 530 hours.
Find the probability of a bulb lasting for at least 552 hours.
Round your answer to four decimal places.

The life of light bulbs is distributed normally. The variance of
the lifetime is 225 and the mean lifetime of a bulb is 520 hours.
Find the probability of a bulb lasting for at most 533 hours. Round
your answer to four decimal places.

USE ONLY EXCEL FOR SOLUTION!
The life of light bulbs is distributed normally. The standard
deviation of the lifetime is 15 hours and the mean lifetime of a
bulb is 590 hours. Using Excel, find the probability of a bulb
lasting for at most 605 hours. Round your answer to four decimal
places.
PLEASE USE ONLY EXCEL AND SHOW FORMULAS USED IN
SOLUTION. THANK YOU!

The lifetime of light bulbs produced by a company are normally
distributed with mean 1500 hours and standard deviation 125
hours.
(c) If three new bulbs are installed at the same time, what is
the probability that exactly two will be burning after 1400
hours?
(d) If three new bulbs are installed at the same time, what is
the probability that at least two will be burning after 1400
hours?
Enter your answer as a decimal, not a percentage. Round...

The
lifetime of light bulbs produced by a company are normally
distributed with mean 1500 hours and standard deviation of 125
hours.
a). What is the probability that a bulb will still be burning
after 1250 hours?
b). What is the number of hours that is survived by 78.81% of
the light bulbs?

Suppose a brand of light bulbs is normally distributed, with a
mean life of 1400 hr and a standard deviation of 50 hr.Find the
probability that a light bulb of that brand lasts between 1315 hr
and 1460 hr.
Areas Under the Standard Normal Curve
z
A
z
A
1.00
.3413
1.50
.4332
1.10
.3643
1.60
.4452
1.20
.3849
1.70
.4554
1.30
.4032
1.80
.4641
1.40
.4192
1.90
.4713
The probability that a light bulb will last between 1315 hr...

Question: Light bulbs have lifetimes that are known to be
approximately normally distributed.
Suppose a random sample of 35 light bulbs was tested, and =
943 hours and s = 33 hours.
a. Find a 90% confidence interval for the true mean life of a
light bulb.
b. Find a 95% lower confidence limit for the true mean life of
a light bulb.
c. Are the results obtained in (a) and (b) the same or
different? Explain why.

It is known that the lifetime of a certain type of light bulb is
normally distributed with
a mean lifetime of 1,060 hours and a standard deviation of 125
hours. What is the
probability that a randomly selected light bulb will last
between 1,000 and 1,100 hours?

An electrical firm manufactures light bulbs that have a lifetime
that is approximately normally distributed with a mean of 800 hours
and a standard deviation of 40 hours. A researcher believes that he
can show that the average lifetime of the bulbs is greater than 800
hours, and from a random sample of 25 bulbs finds that the sample
average lifetime is 820 hours. What should the researcher conclude
about the average lifetime of the bulbs? Be sure to state...

Suppose that the lifetimes of light bulbs are approximately
normally distributed, with a mean of 57 hours and a standard
deviation of 3.5 hours. With this information, answer the
following questions.
(a) What proportion of light bulbs will last more than 61
hours?
(b) What proportion of light bulbs will last 51 hours or
less?
(c) What proportion of light bulbs will last between 58 and 61
hours?
(d) What is the probability that a randomly selected light bulb
lasts...

ADVERTISEMENT

Get Answers For Free

Most questions answered within 1 hours.

ADVERTISEMENT

asked 7 minutes ago

asked 12 minutes ago

asked 15 minutes ago

asked 15 minutes ago

asked 27 minutes ago

asked 28 minutes ago

asked 49 minutes ago

asked 49 minutes ago

asked 55 minutes ago

asked 55 minutes ago

asked 55 minutes ago

asked 56 minutes ago