confidence intervals for a population mean

Select the incorrect statement(s). I. A sampling distribution of sample means is a distribution obtained by using the means computed from random samples of a specific size taken from a population. II. Sampling error is the difference between the sample measure and the ..

The number of vehicles that crossed at a traffic junction per minute at different intervals are: 120, 138, 127, 135, 132, 124, 130, 134. Find the mean and variance. => Mean = 138; Variance = 31.7 or Mean = 130; Variance = 22.3 or Mean = 130; Varianc..

For 99% confidence interval, when t ∝ /2 is 2.878, which of the following could be the sample size? => 19 or 9 or 100 or 18..

In a survey of 500 canned fish, 150 fish has a potassium content of 3800 ppm. Find the 95% confidence interval for the true proportion of canned fish whose potassium content is 3,800 ppm. => 22.7% < p < 37.3% or 26% < p < 34% or 26.3% < p < 33.7% or 66% < p ..

An automobile parts supplier wants to know how long car owners plan to keep their cars with them. A random sample of 20 car owners results in a standard deviation of 3.7 years. Find a 95% confidence interval for the variance and standard deviation. Assume that the variable is no..

A mail order firm professional wishes to estimate the average time taken to deliver the packet(s). How large a sample must she select if she desires to be 90% confident that the true mean is within 3 days of sample mean? The standard deviation of the delivery of packet..

The principal of a school found the mean age of 40 students of one class as 16.50 and that of 50 students of another class as 16. If the standard deviations are 2.83 and 3, find out if their mean ages differ at 99.73% and 98% confidence levels. => the mean ag..

Check whether the population variances differ significantly at 90% confidence. Also find out F-test value. The data relating to two samples from those populations are shown in the table. Sample size Sample variance 25 7 16 5.6 => 2.11, do not differ or 2.29, differ or ..

There are three methods to find mean for a frequency distribution. (i) Direct method: where x is the mid-interval f is the frequency M is the mean (ii) Short-cut method: where A = assumed mean d = x - A (iii) Step-deviation method: where i = class size..

Select the incorrect statement(s). I. If a confidence interval does not include H 0 , then a hypothesis test will reject H 0 . II. If a confidence interval include H 0 , then a hypothesis test will reject H 0 III.For testing H 0 , t distribution is appropriat..