standard deviation

The mean score on a standardized test is 100 with a standard deviation of 8. A random sample of 48 scores was found to have a mean of 98. Find the 95% confidence interval. => The interval is between 97.75 and 102.25 or The interval is between 1.15 and 100 or The interv..

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..

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..

The average monthly insurance premium paid by 15 managers is $90 with a standard deviation of $5. 31 officers pay an average of $65 with the standard deviation of $8.63. At 90% confidence, find the test value. Do the managers pay less average premium than the..

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..

The scores made by candidates in a certain test are normally distributed with mean 500 and standard deviation 100. What percentage of candidates received scores greater than 700? => 2.28% or 2.82% or 47.72% or 47.27%..