Statistics and Probability Answers

Work Interruptions Survey found that out of 300 workers, 245 said they were interrupted three or more times an hour by phone messages, faxes, etc. Find the 90% confidence interval of the population proportion of workers who are interrupted three or more times an hour.

Exercise A: A hog raiser in a certain province uses two meth ods of pig-farming: intensive pig farming, where pigs are housedindoorsin group-housing or straw-lin essheds; andextensive pigfarming, where pigs are allowed to wander around the farm or fence. Test the hypothesis wheth er or not the mean weight of pigs in intensive farmingis better th an the extensive farming based from the mean weight of the pigs in the sample with data shown below. Use a one-tailed test at a = 1%. Inten sive farming: X, = 85 kg, si = 10 kg, and n = 55 Extensive farming: X, = 79 kg, s = 6 kg, and n, = 45

Suppose a book of 585 pages contains 43 types of graphical errors if these errors are randomly distributed throughout the book .what is the probability that 10 pages selected at random will be free from errors

Find the probability of z lying between z=0 and z=2.3.

What is the probability that a hired bike will be deemed beyond repair provided that the wheels get damaged independently of each other

Assume the service life is distributed normally, a random sample of several electronic stuff with a service life (years): 6, 7, 7, 7, 6, 8, 8, 7, 6.

Does this indicate that the average lifespan of a shaker from Onix is not the same as 7

year? Do hypothesis testing with a significance level:

a. 1%

b. 5%

c. 10%

The heights of 2-year-old children are normally distributed with a mean of 32 inches and a standard deviation of 1.5 inches. Pediatricians regularly measure the heights of toddlers to determine whether there is a problem. There may be a problem when a child is in the top or bottom 5% of heights. Determine the heights of 2-year-old children that could be a problem.

The average number of milligrams (mg) of cholesterol in a cup of a certain brand of ice cream is 660 mg, and the standard deviation is 35 mg. Assume the variable is normally distributed.

_______3. If a sample of 10 cups of ice cream is selected, what is the probability that the mean

of the sample will be larger than 670 mg?

A.   11.84%                       B. 14.18%            C. 18.41%           D. 19.41%

_______4. If a sample of 10 cups of ice cream is selected, what is the probability that the mean

of the sample will be smaller than 625 mg?

A.   0.0008%                     B. 0.008%            C. 0.08%             D. 0.8%

_______5. If a sample of 10 cups of ice cream is selected, what is the probability that the mean

of the sample will be larger than 637 mg?

A.   91.28%                       B. 98.12%            C. 98.21%           D. 99.21%

A jar contains 9 red marbles numbered 1 to 9 and 3 blue marbles numbered 1 to 3. A marble is drawn at random from the jar. Find the probability that the marble is red or even-numbered?

 A sample of 100 recorded deaths in the United States during the past year showed an average life span of 71.8 years. Assuming a population standard deviation of 8.9 years,

does this seem to indicate that the average life span today is greater than 70 years? Use a level of significance:

a. 1%

b. 5%

c. 10%