13. A random sample has been taken from a normal distribution and the following confidence intervals are constructed using the same data: (38.02,61.98) and (39.95, 60.05) a) What is the value of the sample mean? b) One of these intervals is a 95% CI and the other is a 90% CI. Which one is the 95% and why?

Q4. Identify the incorrect statement below: The estimator, X from a random sample of X A. Is the mean of the population of X. B. Is an unbiased estimator of the population mean. C. Has an expected value equal to the mean of X. D. Is a random variable with a variance smaller than the variance of X. O A. A ОВ. В С. С O D. D

I. There are two samples with means 15 and 18. Both of those samples consist of 24 observations. Sample standard deviations are equal to 4 in both cases. If you want to test whether the difference between the mean in the first and the mean in the second population is equal to 0, what is your decision at the .01 level?

14.

Which type of confidence interval should you use in this situation? A sample of 25 different payroll departments found that the employees worked an average of 310.3 days a year with a standard deviation of 23.8 days. The distribution is approximately normally distributed. Find the 90% confidence interval for the average days worked of all payroll departments.   Question 2 options:   1)  a confidence interval for the mean using a table value from the standard normal distribution.   2)  a confidence interval for the mean using a table value from the t distribution.   3)  a confidence interval for a proportion using a table value from the standard normal distribution.   4)  a confidence interval for proportion using a table value from the t distribution.   5)  none of the above.

9 The standard error of the mean is, a 0.881       b 0.735       c 0.612       d 0.510

answer d)

Pavan.88.9

T. Q 4.