what are class intervals

A vehicle travels 118 miles in 3 hours. What is its average velocity over the entire 3 hours time interval? => 39.33 miles/hour or 354 miles/hour or 115 miles/hour or 0.03 miles/hour..

From the stem-and-leaf plot, find how many data values are less than 93, from the intervals 80 - 89, 90 - 99, 100 - 109, and 110 - 119. => 6 or 3 or 4 or 5..

Based on the stem-and-leaf plot, how many data items are there in the intervals 20 - 29, 30 - 39, 40- 49, 50- 59 and 60 - 69? => 17 or 19 or 23 or 22..

From the stem-and-leaf plot, find how many data values are less than 100, from the intervals 80 - 89, 90 - 99, 100 - 109 and 110 - 119. => 8 or 9 or 6 or 7..

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 375 or 65 or..

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 and 34 or b..

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 < 1,550.4 or 91..

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 between 1..

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. => 122 &l..

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 < σ ..