finding confidence intervals

A survey of 120 families showed that at least 78 had a computer at home. Find the 99% confidence interval of the true proportion of families who own a home computer. => 64.5% < p < 65.5% or 5.38% < p < 7.62% or 53.8% < p < 76.2% or 60.6% < p < 6..

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..

A survey of 156 people showed that 104 go for a brisk walk daily. Find the 99% confidence interval of the true proportion of people who go for a brisk walk. => 57.3% < p < 76.7% or 63.2% < p < 70.8% or 66.6% < p < 67.4% or 66% < p < 70%..

An investigation was done to examine the proportion of male teenagers who smoke. From a pilot study, it was found that out of 150 males, 40 smoked. Find the 99% confidence interval of the true proportion of teenagers who smoke. => 16.05% < p < 37.95% or 17.6% <..

A random sample of 100 similar iron bars manufactured at a factory had a mean diameter of 6.43 mm and a variance of 0.032 mm 2 . Find 95% confidence interval and 99% confidence interval. Which interval is smaller? => (6.40, 6.47) and (6.38..

A study of 50 basket ball players showed that their scoring average is 15.8 points per game. The 90% confidence interval of the mean score for all players is between 14.1 and 17.5. Find the 90% confidence interval of the mean score(μ) if 100 play..

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 2..

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 be..

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 &l..

The number of miles per hour driven by a sales person on 14 different days is listed here. What is the point estimate for the mean? Find the 95% confidence interval of the mean for the average miles per hour. => 32.3 and 29.5 < μ < 35.1 or 31.5 and 31 < &mu..