Answer and explain the reason with showing work

4. Suppose that you have a random sample of 21 individuals. The sample mean for years of education completed is 12.8 years with a sample standard deviation of 2.1 years. Suppose someone claims that the population standard deviation is greater than 1.5 years. The test statistic associated with this test is and the null hypothesis at the 5-percent level of significance. Note that the one-tailed chi-squared 5-percent critical value is 31.4. A. 39.2; cannot be rejected. B. 39 2; can be rejected. 28; cannot be rejected. 28; can be rejected. Suppose that the 99-percent two-sided confidence interval for a mean is -20 to 50. The sample mean A. cannot be computed without knowing the sample size. cannot be computed without knowing the standard error. cannot be computed without knowing both the sample size and the standard errors. D. is 15. Suppose that the underlying population is normally distributed. From a random sample of 16 individuals from this population, the sample mean is 8 and the sample standard deviation is 10. Suppose someone claims that the true population mean not equal to 5. The value of the t-test statistic is and the null hypothesis be rejected at the 10-percent level of significance. 1.2: cannot 1.8; can 2: can 3.2; cannot Which of the following is a criterion for choosing a t-test rather than a Z-test when making an inference about the mean of a population? A. the population mean is unknown. the sample size is unknown. the population standard deviation is unknown the null hypothesis is unknown