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. State the null hypothesis and alternative hypothesis. => H o : The mean score = 100, H a : The mean score ≠ 100 or H o : The mea..

The local authorities in a certain city install 1600 electric lamps in the streets of the city. If the lamps have a mean life rate of 1000 burning hours, with a standard deviations of 150 hours, find the value of - 2 standards deviations form the mean. Assume..

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..

The university authorities wanted to estimate the average age of the students in their university by taking a random sample of 25 students. The standard deviation was found to be 3 years. Find the 95% confidence interval for the variance (σ 2 ) and standard ..

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 of the r..

The distances traveled in kilometers by a person on four different days is: 63, 42, 55, 40. Find the mean distance and standard deviation. => Mean = 54, standard deviation = 9.5 or Mean = 54, standard deviation = 6.3 or Mean = 50, sta..

The probability distribution for the number of clients visiting a bookshop daily is presented as under. Find the mean and the standard deviation of the distribution. What is the expected number of clients visiting the bookshop? => mean = 67.66, standard deviationh..

60% of the people in a community are eligible to vote. If 100 people are selected at random, then find the standard deviation of the number of people who are eligible to vote. => 24 or 4.89 or 60 or 40..

The average price of a computer is $750. If prices of computers are approximately normally distributed with a standard deviation of $75, then what is the probability that a randomly selected computer costs more than $1000? => 3.3% or 0.33% or 0.04% or 0.4%..

The scores made by candidates in a certain test are normally distributed with mean 500 and standard deviation 100. What is the percentage of candidates who scored less than 400? => 15.87% or 17.85% or 18.57% or 15.78%..