standard deviation formula

The 95% confidence interval for the mean number of tablets in a bottle of calcium tablets is between 149.04 and 150.96. The standard deviation is 3 tablets. Find the size of the random sample that was used to determine this interval. => 40 or 38 or 6 or 150..

The 95% confidence interval for the mean weight of a sack of potatoes is between 4.92 and 5.08. If a random sample of 32 sacks was used to determine this interval, what was the standard deviation? => 0.04 or 0.16 or 3.92 or 0.23..

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..

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%..

In a study of reaction time (in seconds) to a medicine given to 5 cancer patients, an Oncologist recorded the data 10, 20, 30, 25, 15. Find the standard deviation. => 7.1 or 50 or 20 or 15.81..

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..

In a survey it was found that 20% of people living in a society watch channel A. If a random sample of 120 people is selected, then find the standard deviation of the number of people in the sample who watch channel A. => 24 or 19.2 or 4.38 or 96..

Suppose the number of games in which major league baseball players play during their careers is normally distributed with mean equal to 1,500 and standard deviation equal to 350 games. What percentage play in fewer than 750 games? => 98.39% or 1.62% or 48.39% or 51.62%..