4. A sample of 81 tech firms indicated that they experience an average of 278 cyber...

Question

Question

Answer 1

Answer #1

The confidence interval (CI)can be calculated using the formula

CI = X^ ⁺ Z ( s\sqrt n)

Where,

X^ = the mean = 278

Z = the z value for 90% confidence interval = 1.645

s = the standard deviation = 28.5

n = number of observations = 81

sqrt n = square root of n = 9

Therefore, substituting the values, we get

CI = 278 + 1.645(28.5 \ 9)

= 278 + 5.21

Confidence interval = 272.79 to 283.21

Answer 2

Similar Homework Help Questions

10) A sample of 50 cars on a section of the interstate indicated that the average...

10) A sample of 50 cars on a section of the interstate indicated that the average speed was 75.34 miles per hour. The sample standard deviation was 4.43 miles. Calculate a 90% confidence interval for the average speed on the section of interstate.
The mean diastolic blood pressure for a random sample of 60 people was 81 millimeters of...

The mean diastolic blood pressure for a random sample of 60 people was 81 millimeters of mercury. If the standard deviation of individual blood pressure readings is known to be 12 millimeters of mercury, find a 90% confidence interval for the true mean diastolic blood pressure of all people. Then complete the table below. Carry your intermediate computations to at least three decimal places. Round your answers to one decimal place. What is the lower limit of the 90% confidence...
1. A random sample of 37 employees in Sweden worked an average number of 231 days...

1. A random sample of 37 employees in Sweden worked an average number of 231 days per year. The sample standard deviation is 26 days. a) Develop a 95% confidence interval for the average number of work-days per year for all Swedish employees. (6 marks) b) Verbally interpret the meaning of the confidence interval that you found for part a) c) If the desired margin of error for the above confidence interval is 4 days, what size sample is necessary?...

In a random sample of 81 audited estate tax returns, it was determined that the mean...

In a random sample of 81 audited estate tax returns, it was determined that the mean amount of additional tax owed was $3409 with a standard deviation of $2533. Construct and interpret a 90% confidence interval for the mean additional amount of tax owed for estate tax returns.
In a random sample of 81 audited estate tax returns, it was determined that the mean...

In a random sample of 81 audited estate tax returns, it was determined that the mean amount of additional tax owed was $3487 with a standard deviation of $2592 Construct and interpret a 90% confidence interval for the mean additional amount of tax owed for estate tax returns.
The Highway Safety Department wants to study the driving habits of individuals. A sample of 81...

The Highway Safety Department wants to study the driving habits of individuals. A sample of 81 cars traveling on the highway revealed an average speed of 67 miles per hour with a standard deviation of 9 miles per hour. a. Compute the standard error of the mean. b. Determine a 99% confidence interval estimate for the speed of all cars.

The average time to drive from Joliet to Chicago in non-rush hour traffic on I 55...

The average time to drive from Joliet to Chicago in non-rush hour traffic on I 55 is 48 minutes with a sample standard deviation of 6.3 minutes. For n = 65, find the 95% confidence interval for the mean. Meijer has 10 lbs. of potatoes on sale for Thanksgiving. If the bags have a population standard deviation of .75 lbs., find the 90% confidence interval for the mean for n = 50. At JJC, 125 out of 200 students take...
In a random sample of 81 audited estate tax returns, it was determined that the mean...

In a random sample of 81 audited estate tax returns, it was determined that the mean amount of additional tax owed was $3447 with a standard deviation of $2590. Construct and interpret a 90% confidence interval for the mean additional amount of tax owed for estate tax returns. The lower bound is = (Round to the nearest dollar as needed)
24. A supplier sells synthetic fibers to a manufacturing company. A simple random sample of 81...

24. A supplier sells synthetic fibers to a manufacturing company. A simple random sample of 81 fibers is selected from a shipment. The average breaking strength of these is 29 lb, and the standard deviation is 9 lb. The number of fibers that must be sampled so that a 99%confidence interval specifies the mean to within ±1 lb is nearly ___________.

2. A random sample of 100 graduates of a certain secretarial school typed an average of...

2. A random sample of 100 graduates of a certain secretarial school typed an average of 90 words per minute with a sample standard deviation (s) of 10 words per minute. We assume a normal distribution for the number of words typed per minute. (a) (4pts) Find a 95% confidence interval for the average number of words t yped per minute of all graduates of this school. (b) (3pts) Suppose the population standard deviation (o) is exactly 10 words per...