mean in normal distribution

What formula is used to gain information about a sample mean when the variable is normally distributed or when the sample size is 30 or more? => z = X - μ σ or z = X ‾ - μ σ n or z = X ‾ - μ σ n or z = X - μ σ..

Find the lowest control limit for a normally distributed curve with a mean of 15 and a standard deviation of 2.5. => 12.5 or 10 or 7.5 or 22.5..

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%..

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%..

In an aptitude test conducted to qualify for a job, the scores given were normally distributed with a mean of 75 and a standard deviation 8. If only top 15% were to be selected, then find the cut - off scores. => 83.8 or 88.3 or 83.3 or 85..

Students of a class were given an aptitude test. Their scores were found to be normally distributed with mean 65 and standard deviation 7. What percent of the students scored between in the range 51 - 72? => 47.72% or 81.85% or 34.13% or 13.59%..

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...

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%..

To qualify as a contestant in a swimming event, a swimmer has to be in the top 20% of all entrants. The swimming times are normally distributed, with a mean of 70 min and a standard deviation of 3 min. What is the qualifying time for the event to the nearest minute? =>..

A survey asks 'How much time do you spend in front of the TV in one week? Suppose the responses are normally distributed, the mean is 10 hours and the standard deviation is 2 hours. What value in hours is one standard deviation above the mean, and one standar..