standard deviation

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 which differ from 500 by more than 150 points? => 43.23% or 13.36% or 43.32% or 6.68%..

55% of the students passed in an online examination. If 600 students are selected at random, then find the variance and standard deviation of the number of students passing the examination. => 148.5, 12.19 or 330, 12.19 or 330, 148.5 or 12.19, 148.5..

A machine produces bolts, of which 10% are defective. Find the probability that in a random sample of 400 bolts produced by the machine, 55 or more will be defective. Assume a standard deviation of 6. => 0.970 or 0.0079 or 0.079 or 0.0097..

If two samples have means of 24 and 28 and standard deviations of 4 and 6, with 12 and 15 as the sizes, find the z score for difference of two population means. => 2.07 or 7.73 or 1.07 or 1.93..

In a random sample of 25 trees, the variance in height was found to be 6.9. Find the 95% confidence interval for the standard deviation. Assume that the variable is normally distributed. => between 4.9 and 13.7 or between 4.2 and 13.4 or between 5.5 and 14.1 or between 5.5 and 1..

A standard notebook is supposed to have on an average, 200 pages, with a standard deviation of 2 pages. From a supply of 2500 notebooks, a random sample of 40 notebooks was taken and found that the mean number of pages in the notebook was 197. Determine the standa..

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 shoe sizes of 10 students in a class are 4, 3, 5, 6, 3, 6, 5, 4, 3, 6. Find the variance ad standard deviation of the data. σ => Variance = 1.45; Standard deviation = 1.1 or Variance = 1.45; Standard deviation = 1.2 or Variance =..

40% of the people in a town X used the library last year. If 750 people are selected at random, then what is the standard deviation of the number of people who used the library last year? => 13.4 or 180 or 300 or 134..

Mr. John gave his students a test in the class. The scores were normally distributed with a mean of 75 and standard deviation of 4. What percent of the students scored between 71 and 79? => 95% or 99.7% or 68% or 34%..