# statistics

posted by .

2. The new Twinkle bulb has a standard deviation hours. A random sample of 77 light bulbs is selected from inventory. The sample mean was found to be 492 hours.
a. Find the margin of error E for a 90% confidence interval.

• statistics -

Margin of error = z-value (sd/√n)

Find the z-value corresponding to 90% confidence using a z-table.

sd = standard deviation
n = sample size

I hope this will help get you started.

• statistics -

Please someone help me? The new twinkle bulb has a standard deviation 35 hours. A random sample of 50 light bulbs is selected from inventory. The sample mean was found to be x=500 hrs. Find the margin of error for 95%, construct a 95% confidence interval for the mean life of all Twinkle bulbs. I am desperate.

## Similar Questions

1. ### statistics

1. The new Twinkle bulb has a standard deviation σ = 34 hours. A random sample of 77 light bulbs is selected from inventory. The sample mean was found to be x= 492 hours. Question: Find the margin of error E for a 90% confidence …
2. ### statistics

The new Twinkle bulb is being developed to last more than 1000 hours. A random sample of 100 of these new bulbs is selected from the production line. It was found that 48 lasted more than 1000 hours. Find the point estimate for the …
3. ### statistics

Solve the problem. The lifetime of a new brand of light bulb can be described by a Normal model with a mean of 2000 hours and a standard deviation of 250 hours. Find the percentage of light bulbs that will last more than 2600 hours. …
4. ### math

The new Twinkle bulb is being developed to last more than 1000 hours. A random sample of 100 of these new bulbs is selected from the production line. It was found that 48 lasted more than 1000 hours. Find the point estimate for the …
5. ### 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
6. ### 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 …
7. ### Statistics

Can anyone tell me how to use TI-84 calculator to solve this problem?
8. ### Statistics

A company has developed a new type of light bulb, and wants to estimate its mean lifetime. A simple random sample of 12 bulbs had a sample mean lifetime of 692 hours with a sample standard deviation of 30 hours. It is reasonable to …