normal distribution

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..

Determine whether the data is normally distributed or skewed. 12, 11, 10, 11, 11, 11, 12, 12, 12, 12, 10, 12, 13, 13, 13, 13, 9, 13, 8. => normally distributed or negatively skewed or cannot be determined or positively skewed..

Monthly expenditures for a family of four in a city averages $450, with a standard deviation of $65. Assume the monthly expenditures are normally distributed. Find the probability that a family whose expenditure will be between $385 and $515. => 0.3413 or 0.6826 or 0.3143 or 0.6..

Monthly expenditures for a family of four in a city averages $450, with a standard deviation of $65. Assume the monthly expenditures are normally distributed. What is the percentage of families whose expenditure is between $437 and $476? => 7.93% or 82% or 23.47% or 15.54%..

A truck was loaded with sacks of onions whose weights were normally distributed with a mean of 35 lb and a standard deviation of 2 lb. What is the probability that a sack of onions will weigh more than 37 lb? => 0.1857 or 0.3143 or 0.1587 or 0.3413..

Five thousand candidates appeared for an examination, which carried a maximum of 100 points. These points were found to be normally distributed with mean 39.5 and standard deviation 12.5. Determine approximately the number of candidates who secured more than 60 points. => 121 or..

To qualify in a competitive examination, candidates must score in the top 5% in the examination. The test has a mean of 200 and a standard deviation of 20. What is the lowest possible score to qualify? Assume the test scores are normally distributed. => 202.6 or 200 or 232.9 or ..

Suppose that for the past 15 years the variance for the number of skydivers met with accident each year has been 16. Find the 90% confidence interval for the true variance. Assume that the variable is normally distributed. => between 9 and 31 or between 11 and 39 or between 10 a..

The readings of diastolic blood pressure of a group of volunteers for a medical experiment were normally distributed with a mean of 82 and a standard deviation of 8. If volunteers are to be selected from the middle 50% group, then find the upper and the lower readings, which qua..

A sample of 30 RAM chips was tested for the average access time. The standard deviation was found to be 2 nanosec. Find the 90% confidence interval for the true standard deviation. Assume that the variable is normally distributed. => between 1.7 and 2.6 or between 1.6 and 2.5 or..