« previous next »

Author Question: In using the standard normal distribution to construct a confidence interval for the population ... (Read 96 times)

cagreen833

  • Hero Member
  • *****
  • Posts: 544
on: Jun 24, 2018
In using the standard normal distribution to construct a confidence interval for the population mean, what assumptions are necessary if the sample size n is less than 30?

Question 2

A city-paid consumer advocate wants to secure information about the mean length, , of coin-separated car wash cycles. A previous study reported the standard deviation of the length of car wash cycles to be 6 minutes. The advocate timed the wash cycle at 81 randomly selected car wash locations and the mean of the sample was 4.8 minutes. The 90 percent confidence interval estimate is 3.70 to 5.90 minutes. Interpret this interval.


emily12345

  • Sr. Member
  • ****
  • Posts: 321
Reply #1 on: Jun 24, 2018
Answer to Question 1

In this case, we need to assume that the population is normally distributed and the population standard deviation  is known.

Answer to Question 2

We have 90 confidence that the population mean is included in this interval.


Related Topics

Need homework help now?

Ask unlimited questions for free

Ask a Question
« previous next »
 

Did you know?

Though the United States has largely rejected the metric system, it is used for currency, as in 100 pennies = 1 dollar. Previously, the British currency system was used, with measurements such as 12 pence to the shilling, and 20 shillings to the pound.

Did you know?

If you could remove all of your skin, it would weigh up to 5 pounds.

Did you know?

GI conditions that will keep you out of the U.S. armed services include ulcers, varices, fistulas, esophagitis, gastritis, congenital abnormalities, inflammatory bowel disease, enteritis, colitis, proctitis, duodenal diverticula, malabsorption syndromes, hepatitis, cirrhosis, cysts, abscesses, pancreatitis, polyps, certain hemorrhoids, splenomegaly, hernias, recent abdominal surgery, GI bypass or stomach stapling, and artificial GI openings.

Did you know?

Excessive alcohol use costs the country approximately $235 billion every year.

Did you know?

Dogs have been used in studies to detect various cancers in human subjects. They have been trained to sniff breath samples from humans that were collected by having them breathe into special tubes. These people included 55 lung cancer patients, 31 breast cancer patients, and 83 cancer-free patients. The dogs detected 54 of the 55 lung cancer patients as having cancer, detected 28 of the 31 breast cancer patients, and gave only three false-positive results (detecting cancer in people who didn't have it).

Population Interactions and Communities Population Interactions and Communities
Features of a normal 12-lead ECG. Features of a normal 12-lead ECG.
Hematocrits, left to right: normal, anemia, polycythemia. Hematocrits, left to right: normal, anemia, polycythemia.
Sources of income for U.S. population aged 65 and over. Sources of income for U.S. population aged 65 and over.
The typical distribution of neurofibrillary tangles and amyloid plaques in the brains of patients ... The typical distribution of neurofibrillary tangles and amyloid plaques in the brains of patients ...
The developing and emerging nations have high rates of population growth The developing and emerging nations have high rates of population growth
Video: Ventilation - phases and driving forces

For a complete list of videos, visit our video library