what are class intervals

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% < p < 36.4% or 21..

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 ..

In the given stem-and-leaf plot, find how many data values are greater than 102, from the intervals 80 - 89, 90 - 99, 100 - 109, and 110 - 119. => 4 or 5 or 3 or 2..

Identify the interval level of data. I. height II. nationality III. age IV. IQ V. time => II only or IV only or V only or III, IV and V only..

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. => 45 or ..

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 12..

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 sample si..

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 < 98.01 o..

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, 49.51) and..

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 < 28 or 1..