Determine the estimate of the population mean and a 95% confidence interval about the point estimate. No statements are made about the quality or precision of a point estimate. It has no sampling distribution. The mean of the four values is 33.275 Mpa. The sample standard deviation, s, is 1.08 MPa, which we will need for the confidence interval calculation. Interval Estimate ofμ Interval Estimate of a Population Mean: σKnown xz n ± α σ /2 where: is the sample mean 1 -αis the confidence coefficient zα/2 is the z value providing an area of α/2 in the upper tail of the standard normal probability distribution σ is the population standard deviation n is the sample size x A point estimate is a value of a sample statistic that is used as a single estimate of a population parameter. Point estimation. Statisticians prefer interval estimates because interval estimates are accompanied by a statement… 2. The size of the population is only relevant if it is particularly small. Point and Interval Estimation: To estimate an unknown parameter of the population, concept of theory of estimation is used.There are two types of estimation namely, 1. Interval estimation . If repeated random samples were taken from the population, the point estimate would be expected to vary from sample to sample. A confidence interval is an estimate constructed on the basis that a specified proportion of the confidence intervals include the true parameter in repeated sampling. Point and Interval Estimation . It is an estimate based on only a single random sample. For example, we say that the sample mean X is an estimator of the population mean m and the computed value x of X is an estimate of m. The estimator is a sampling random variable and the estimate is a number. Point estimates are subject to bias, where the bias is the difference between the expected value of the estimator and the true value of the population parameter involved. Each point estimate has a well-defined formula used in its calculation. Interval Estimates A confidence interval (CI) is a range of values within which the population parameter is expected to occur. This is the point estimate of the mean. To calculate a confidence interval, you need a point estimate, a standard score, the standard deviation (or an estimate of it), and the sample size. For example, our best estimate of the population mean is the value $32,640 (the point estimate) and our 95% confidence interval is $30,913.71 to $34,366.29. The sample size is needed because the variance of the point estimate is inversely proportional to the sample size. A point estimate is one value (a single point) used to estimate a population parameter. Point Estimation. 1. By the way, note that the bigger your sample size, the more narrow the confidence interval will be. 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