# Statistics

posted by .

The lifetimes of batteries produced by a firm are known to be normally distributed with a mean of 100 hours and a standard deviation of 10 hours. What is the probability a battery will last between 110 and 120 hours?

• Statistics -

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.

• Statistics -

The lifetime (in years) of 9 automobile batteries of a certain brand are: 2.4, 1.9, 2.0, 2.1, 1.8, 2.3, 2.1, 2.3, 1.7. At alpha O.05 level of significance, test if the mean battery life is less than 25 years.
State the null and alternative hypothesis.
Give a conclusion for the confidence interval

## Similar Questions

The lifetimes of lightbulbs of a particular type are normally distributed with a mean of 290 hours and a standard deviation of 6 hours. What percentage of the bulbs have lifetimes that lie within 1 standard deviation to either side …
2. ### statistics

The numbers of hours of life of a torch battery is normally distributed with a mean of 150 hours and standard deviation of 12 hours. In a quality control test, two batteries are chosen at random from a batch. If both batteries have …
3. ### statistics

The lifetime of a 2 volt non-rechargeable battery has a normal distribution with a mean of 516 hours and a standard deviation of 20 hours. What is the z- score for batteries with lifetimes of 520 hours
4. ### statistics

The lifetime of a 2 volt non- rechargeable battery has a normal distribution with a mean of 516 hours and a standard deviation of 20 hours.What is the z- score for batteries with lifetimes of 600 hours
5. ### statistics

The lifetime of a 2- volt non- rechargeable battery in constant use has a normal distribution with a mean of 516 hours and a standard deviation of 20 hours. What is the z-score for batteries with lifetimes of 600 hours?
6. ### statistics

A company produces batteries whose lifetimes are normally distributed with a mean of 100 hours. It is known that 90% of the batteries last at least 40 hours. (i). Estimate the standard deviation lifetime. (3 marks) (ii). What percentage …
7. ### Math

The batteries from a certain manufacturer have a mean lifetime of 890 hours, with a standard deviation of 90 hours. Assuming that the lifetimes are normally distributed, complete the following statements.
8. ### Statistics

The lifetimes of projector bulbs of a particular type are normally distributed with a mean of 470 hours and a standard deviation of 15 hours. What percentage of the bulbs has lifetimes that lie within 2 standard deviations of the mean …
9. ### Statistics

The lifetimes of projector bulbs of a particular type are normally distributed with a mean of 470 hours and a standard deviation of 15 hours. What percentage of the bulbs has lifetimes that lie within 2 standard deviations of the mean …
10. ### statistics

The lifetimes of light bulbs of a particular type are normally distributed with a mean of 370 hours and a standard deviation of 5 hours. What percentage of bulbs has lifetimes that lie within 1 standard deviation of the mean on either …

More Similar Questions

Post a New Question