A manufacturer bonds a plastic coating to a metal surface. A random sample of nine observations on the thickness of this coating is taken from a week’s output, and the thicknesses (in millimeters) of these observations are as follows:19.8  21.2  18.6  20.4  21.6  19.8  19.9  20.3  20.8Assuming normality, find a 90% confidence interval for the population variance.

The following statistics are computed by sampling from three normal populations whose variances are equal: (You may find it useful to reference the table and the g table.) = 30.1, n₁ = 7; 2 = 35.5, n2 = 9; 3 = 40.9, n3 = 4; MSE = 25.0 a. Calculate 95% confidence intervals for H1 H2, H1 - Hз, and μ2 - μз to test for mean differences with Fisher's LSD approach. (Negative values should be indicated by a minus sign. Round final answers to 2 decimal points.) Population Mean Differences H1-H2 H1 H3 H2 H3 Confidence Interval Can we conclude that the population means differ?

A hotel chain wants to estimate the mean number of rooms rented daily in a given month. The population of rooms rented daily is assumed to be normally distributed for each month with a standard deviation of 240 rooms. During February, a sample of 25 days has a sample mean of 370 rooms. The critical value for a 90% confidence interval for this sample is ________.   Question 12 options:   1)  2.58   2)  1.96   3)  2.649   4)  1.645

A study was done using a treatment group and a placebo group. The results are shown in the table. Assume that the two samples are independent simple random samples selected from normally distributed​ populations, and do not assume that the population standard deviations are equal. Complete parts​ (a) and​ (b) below. Use a 0.05 significance level for both parts.     Treatment Placebo   μ μ1 μ2 n 27 39 x 2.38 2.65 s 0.87 0.61 a. Test the claim that the two samples are from populations with the same mean.   What are the null and alternative​ hypotheses?     A. H0​: μ1≠μ2 H1​: μ1<μ2   B. H0​: μ1<μ2 H1​: μ1≥μ2   C. H0​: μ1=μ2 H1​: μ1>μ2   D. H0​: μ1=μ2 H1​: μ1≠μ2 Your answer is correct. The test​ statistic, t, is   ​(Round to two decimal places as​ needed.)