statistics

posted by .

A laptop computer manufacturer found that by improving their battery design, they could increase the time that the laptop computer could be used on a single charge. To verify this improvement, they compared a sample of 10 laptops installed with the improved batteries to a control group of 10 laptops installed with current batteries. After subjecting each laptop to a predetermined set of operations until it ceased to operate, they found that the average lifespan of the improved battery was 4.31 hours, and that the average lifespan of the current battery was 3.68 hours. Correspondingly, the sample standard deviation for the improved batteries was 0.17 hours for the improved group and the sample standard deviation for the current group was 0.22 hours.

Assuming that the two groups have unequal variances, calculate the t-statistic that tests the null hypothesis that the mean lifespan of the two types are equal against the alternative hypothesis that the mean lifespan for the improved batteries is greater than that for the current batteries.
a)1.62
b)7.166
c)-3.682
d)6.907
e)4.923

• statistics -

Welch's t-test for unequal variances:

t = (mean1 - mean2)/√(s^2/n1 + s^2/n2)

t = (4.31 - 3.68)/√(0.17^2/10 + 0.22^2/10)

t = 0.63/0.08792 = 7.166 (rounded)

Similar Questions

1. Intro. to Comp. -- Question

If you need a computer to carry with you to manage your daily schedule of meetings, which type of computer would be ideal in this instance?
2. Vocabulary

Does this sentence demonstrate the correct usage of the word "contrast"?
3. algebra

Susie purchased a laptop computer for \$2000 at the beginning of the year in 2008,the value of the computer decreased by 20% each year. Susie wants to purchase a new laptop computer when the value of hers falls below \$500. When will …
4. statistics 3

An airline promotion to business travelers is based on the assumption that no more than two-thirds of business travelers use a laptop computer on overnight business trips. 1. What is the sample proportion from an American Express-sponsored …
5. statistics 3

An airline promotion to business travelers is based on the assumption that no more than two-thirds of business travelers use a laptop computer on overnight business trips. 1. What is the sample proportion from an American Express-sponsored …
6. Statistics 3

An airline promotion to business travelers is based on the assumption that no more than two-thirds of business travelers use a laptop computer on overnight business trips. 1. What is the sample proportion from an American Express-sponsored …
7. statistics 3

An airline promotion to business travelers is based on the assumption that no more than two-thirds of business travelers use a laptop computer on overnight business trips. 1. What is the sample proportion from an American Express-sponsored …
8. Statistics

a laptop manufacturer finds that the average time it takes an employee to load a laptop with software is 20 minutes with a standard deviation 8 minutes. suppose you take a random sample of 81 employees. the standard deviation of the …
9. algebra

A laptop computer is purchased for \$5000 . Each year, its value is 70% of its value the year before. After how many years will the laptop computer be worth \$300 or less
10. Math

Elizabeth wants to buy a new laptop computer, but she just started her baby sitting job and she hasn't earned any money yet. She figures once she starts earning income she save \$90 a month in a saving account that earns three percent …

More Similar Questions