Stats Help for College-level Students

Determining the standard deviation using a confidence level.

A company claims the standard deviation in their delivery time is less than five days. A sample of 27 past customers is taken. The average delivery time in the sample was 14 days with a standard deviation of 4.5 days. At 95% confidence, test the companies claim.

Calculating the probability from a given situation using mean and the standard deviation.

Brake Pads- A brake pad manufacturer claims its brake pads will last for 38,000 miles. You work for a consumer protection agency and you are testing this manufacturer's brake pads. Assume the life spans of the brake pads are normally distributed. You randomly select 50 brake pads. In your tests, the mean life of the brake pa ...continues

Normal Approximations to Binomial Distributions

A survey of workers in the U.S. found that 2.9% work more than 70 hours per week. You randomly select 10 workers in the U.S. and ask each if he or she works more than 70 hours per week. a)find the probability that at most three people say they work more that 70 hours per week b)find the probability that at least three peopl s ...continues

Testing a claim from a data set.

Use the data set below to test the claim that more than 50% of the are at least 415. data set 350,527,480,410,360,470,390,510,430,452,341,385,380,409,500,377,400,380,420,460

Calculating the probability from a given situation.

An instructor has a test bank consisting of 300 easy true-false questions, 200 difficult true-false questions, 500 easy multiple choice questions and 400 difficult multiple choice questions. If a question is selected at random from the test bank, what is the probability that it will be: a) An easy question b) An easy multipl ...continues

Probability

A manager must select from among ten persons to fill four job openings. Four of the candidates belong to a minority group. If the four positions are filled at random by the candidates, what is the probability that no minority group member will be selected?

Hypothesis Testing

The Boston Weather Services (BWS) says that the mean high temperature for October in a city is 56E F. You believe that it is lower. A sample of 31 mean October temperatures yields mean 54.0E F and standard deviation 5.6 E F. Test the BWS claim at V = 0.01.

Hypothesis Testing

Test the claim the : = 74.1 at V = 0.01 where n = 14, sample mean is 79.0 and sample standard deviation is 5.6. Please explain by using the traditional methods for testing hypotheses and showing the results of all steps in the process.

Testing the claim.

A cereal company claims that the weight of the cereal in one of its packages is at least 14 oz. Eight packages are tested and the weights are given below. Test the claim at V = 0.01. 14.6, 13.8, 14.1, 13.7, 14.0, 14.4, 13.6, 14.2 Please explain by using the traditional methods for testing hypotheses and showing the re ...continues

Confidence Interval

The null hypothesis is V = 72.4 and alternative hypothesis is V does not equal 72.4. The sample mean is 68.325 and sample standard deviation is 14.172 from a sample of size 45. Find the 95% confidence interval. Show the results of all steps in the process.