confidence intervals

The 95% confidence interval for the mean number of mangoes in a carton is between 48.12 and 51.88. If a random sample of 27 cartons were used to determine this interval, what was the standard deviation? => 2 or 3 or 4 or 5..

The 95% confidence interval for the mean number of sheets of paper in a ream is between 452.76 and 447.24. If the standard deviation is 10 papers, find the size of the random sample that was used to determine this interval. => 5.52 or 50 or 1.41 or 7.09..

A recent study of 50 people in a city found that 70% of the people have less than average incomes for the city. How many people should be surveyed to estimate the true proportion of people having an income of less than average with a 99% confidence interval 4% wide? => 874 or 37..

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 between 10 a..

Find the 95% confidence interval for the mean number of people working in night shifts in different parts of the cities in a particular state. A sample of 35 selected cities is shown. => 920.9 < μ < 1,511.4 or 930.905 < μ < 1,501.375 or 925.9 < μ < 1,5..

A sample of 30 RAM chips was tested for the average access time. The standard deviation was found to be 2 nanosec. Find the 90% confidence interval for the true standard deviation. Assume that the variable is normally distributed. => between 1.7 and 2.6 or between 1.6 and 2.5 or..

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 < μ < 34 ..

The daily water usage (in gallons per person per day) of 10 families of a colony has a variance of 286. Find the 90% confidence interval for the variance and standard deviation. Assume that the variable is normally distributed. => 152 < σ 2 < 774 ; 12 < σ &l..

A recent study of 160 people of a locality in a city found that 39 people were obese. Find the 95% confidence interval of the population proportion of individuals living in that city who are obese. => 17.7% < p < 31.1% or 17% < p < 31% or 21% < p < 27.8% or 24...

A survey of 90 recent fatal traffic accidents showed that 52 were alcohol-related. Find the 90% confidence interval of the true proportion of alcohol-related accidents. => 49.4% < p < 66.6% or 50% < p < 66% or 0.49% < p < 0.66% or 52.8% < p < 63.2%..