confidence intervals

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..

A restaurant owner wishes to find the 99% confidence interval of the mean number of visitors to the restaurant each day. How large the sample must be if he wants to be accurate within 10 persons? A previous study showed that the standard deviation of the visitors was 26 persons...

Find the 95% confidence interval for the variance of the ages of players in a basketball team if a sample of 12 players has a standard deviation of 2 years. Assume the variable is normally distributed. => between 2 and 10 or between 2 and 13 or between 2 and 14 or between 2 and ..

When should the t distribution be used to find a confidence interval for the mean? => When the sample size of population is greater than 30 and the standard deviation is known. or When the sample size of population is less than 30 and the standard deviation is known. or When the..

The number of ATM transactions of a bank per day were recorded at 12 locations in a city. The mean of the sample was 88.5 transactions, with a sample standard deviation of 42. Find the 98% confidence interval of the true mean. => 19.06 < μ < 157.94 or 78.99 < μ &l..

A sample of scores of 250 candidates has a mean of 47.2 with a standard deviation of 18.6. Find 90% and 95% confidence interval of the population mean and determine which is larger? => (45.3, 49.1) and (44.9, 49.5) and 95% or (45.26, 49.14) and (44.89, 49.51) and 90% or (44.89, ..

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 distributed...

The standard deviation of the hemoglobin values (g/100ml) of 10 children is 1.7. Find the 99% confidence interval for the variance and standard deviation. Assume that the variable is normally distributed. => 1.26 < σ 2 < 14.75 ; 1.12 < σ < 3.84 or 1.1 <..

A survey of 2,000 people in a city found 72% of them take bread and butter as their breakfast. Find the 90% confidence interval of the true proportion of people taking bread and butter as their breakfast. => 71% < p < 73% or 71.2% < p < 72.8% or 28% < p < 72% o..