# Probability-Math

posted by .

Please forgive me for posting this for the 3rd time but I really need to learn this:
A researcher conducted a study of the access speed of 45 hard drives and concluded that his maximum error of estimate was 28. If he were to conduct a second study to reduce the maximum error of estimate to 7, about how many hard drives should he include in his new sample?
Select one:
a. 720
b. 45
c. 90
d. 180
Please can someone explain me how to do the above problem.
My working: 28/7 = 4, so 4^2=16
16 x 45 =720.
I am not sure if the above working is correct but please i really need help in learning this problem (question). So, Please can anyone assist me by showing the correct method for this.
Thanks.

## Similar Questions

1. ### English

I'll try to learn how to make a clear voice. I'll try to practice making a speech in my room. I'll try to study hard to go abroad. I'll try to study hard to learn in college in the USA. I'll try to study hard to learn linguistics in …
2. ### math

A computer store sold a total of 300 items last month. The store sold six times as many hard drives as they did CD-ROM drives, and half as many floppy drives as hard drives. Based on this information, how many of each item were sold?
3. ### statistics

A researcher wants to estimate the average time (in minutes) spent in a car daily. This will be done by randomly surveying 300 individuals and calculating the sample mean. Find the probability that the estimate will be in error by …
4. ### statistics

A researcher conducted a study of the access speed of 40 hard drives and concluded that his maximum error of estimate was 15. If he were to conduct a second study to reduce the maximum error of estimate to 5, about how many hard drives …
5. ### Statistics

A researcher wishes to estimate, with 95% confidence, the proportion of adults who have high-speed internet access. Her estimate must be accurate within 4% of the true proportion. A) Find the minimum sample size needed, using a prior …
6. ### statistics

A researcher wishes to estimate with 95% confidence the proportion of adults who have high speed internet access. Her estimate must be accurate within 4% of the true proportion. 1. Find the minimum sample size needed using a prior …
7. ### Algebra

Mitch has 3 tests to study for on Thursday night. He needs to spend twice as much time on Science as English. He also has to study Math and he can learn that in 1/2 the time it takes to study English. He has four hours to study. What …
8. ### Statistics & Probability

A researcher conducted a study of the access speed of 45 hard drives and concluded that his maximum error of estimate was 28. If he were to conduct a second study to reduce the maximum error of estimate to 7, about how many hard drives …
9. ### Statistics & Probability

A researcher conducted a study of the access speed of 45 hard drives and concluded that his maximum error of estimate was 28. If he were to conduct a second study to reduce the maximum error of estimate to 7, about how many hard drives …
10. ### Physics

Physics lab need help with sources of error. In our lab, we had to use carbon tape and a spark timer to find out the maximum velocity and maximum acceleration of a high school student. I'm having a hard time to find sources of errors. …

More Similar Questions