standard deviation formula

Select the incorrect statement(s). I. A sampling distribution of sample means is a distribution obtained by using the means computed from random samples of a specific size taken from a population. II. Sampling error is the difference between the sample measure and the corresponding population measu..

The scores on a certain standardized test are known to have a mean of 100 and standard deviation 25. A person will get a merit certificate if he scores above 125. What is the probability that a person taking this test receives a merit certificate? => 0.1587 or 0.6587 o..

The average age of the accountants at Six Soft Technologies is 24 years, with a standard deviation of 4 years. The average salary of the accountants is $30,000 with a standard deviation of $2,500. Compare the variations of age and income. => income of account..

Two cloth stores design 15 new types of shirts for every three months to attract the customers. The mean number of shirts designed in the first cloth store was 12, with a standard deviation of 4. The mean number of shirts designed in the second cloth store was 20 with a sta..

Assume that the weights of 3,000 students at a university are normally distributed with mean 150 pounds and a standard deviation of 7 pounds. If 100 samples of 30 students each are obtained, then what would be the expected mean and standard deviation? => 150 ..

An automobile parts supplier wants to know how long car owners plan to keep their cars with them. A random sample of 20 car owners results in a standard deviation of 3.7 years. Find a 95% confidence interval for the variance and standard deviation. Assume tha..

Electricity bills (in dollars) of 8 houses are as follows: 70, 82, 76, 79, 83, 85, 72, 77. Find the range and the standard deviation in dollars. => Range = 15; Standard deviation = 4.9 or Range = 15; Standard deviation = 3.4 or Range = 12;..

The average price of a computer is $750. If prices of computers are approximately normally distributed with a standard deviation of $75, then what would be the maximum price of 10% of least-expensive computers? => $654 or $754 or $745 or $645..

Let X denote the number of scores on a test. If X is normally distributed with a mean of 90 and a standard deviation of 10, find the probability that X is not less than 70. => 0.4772 or 0.7472 or 0.7972 or 0.9772..