solve log normal probability distribution

Conclusion - In this chapter we have studied the method of evaluating probabilities of events relating to independent events and conditional events. We have also studied about random variables and their probability distributions, namely binomial distribution ..

The range for the above ungrouped data is 49 - 12 = 37. Normally it is desirable to divide the range into 6 to 10 classes. Consider the class 11 - 15. If a student scores 11 marks or 15 marks, he will be put in this class. For this class, 11 is the lower limit and 15 is the upper limit an..

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%..

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 0.3..

The lifetime of certain kinds of electronic devices have a mean of 350 hours and a standard deviation of 20 hours. The distribution is measured to the nearest hour and can be approximated closely to a normal curve. Find the probability that any one of these devices wil..

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..

A random sample of 81 students was tested for the problem solving approach skills. The variance of the scores obtained from the sample was found to be 144. Find the 80% confidence interval for the variance and standard deviation. Assume that the variable is normally distrib..

The lifetime of an electronic toy is observed as normally distributed curve with a mean of 300 hours and a standard deviation of 180 hours. What is the probability that a randomly selected toy will last for 300 to 480 hours? => 480 or 300 or 0.68 or 0.34..

Find the probability P ( z < - 0.65) using the standard normal distribution. => 25.78% or 28.75% or 27.58% or 74.22%..

The average annual salary in a district is $30,000. Assuming that the salaries were normally distributed for a certain group of wage earners with a standard deviation of $5,000, what is the probability that for a randomly selected sample of 70 earners the mean salary f..