Let T have a (Student's) t distribution with 10 degrees of freedom. If P(T < k) = 0.95, what is the value of k? Let mu be the unknown mean of a Normal distribution. I take 20 observations randomly from this distribution, and want to test H0: mu = 15 vs H1: mu is not equal to 15 at the 5% level of significance. If I observe a p-value of 0.11, what decision can I make?
Write mu for the mean of a Normal distribution. The value of the standard deviation is unknown. We want to test H0: mu = 8 vs H1: mu > 8. A random sample of 15 observations is taken from this distribution, and the sample mean (x-bar) and sample standard deviation (s) are calculated. Then t = (x-bar - 8)/[s/square_root(15)] is calculated, and is found to equal = 1.85. At what levels of significance could we reject H0?
Let T have a (Student's) t distribution with 10 degrees of freedom. If P(T < k)...
Let X1, X2, . . . , Xn be a random sample of size n from a normal population with mean µX and variance σ ^2 . Let Y1, Y2, . . . , Ym be a random sample of size m from a normal population with mean µY and variance σ ^2 . Also, assume that these two random samples are independent. It is desired to test the following hypotheses H0 : σX = σY versus H1 : σX...
K=42,n=1,m=18 8. The amount of time it takes a student to solve a homework problem in mathematical statistics (in minutes) follows a normal distribution with unknown mean μ and a variance equal to 9m2. Find the most powerful test to verify the null hypothesis that μ k against the alternative that , 2k on the base of k independent observations, for a significance level of n%. Calculate the power of this test (for the alternative hypothesis). What is the decision,...
If, in a sample of n = 16 selected from a normal population, x bar = 57, and s = 8, what are the critical values of t if the level of significance, is .01, the null hypothesis h0 is mu = 50, and the alternative hypothesis H1 is mu is not equal to 50. The critical values of t are +/- ___ , ____.
Suppose you want to test the following hypotheses: H0: p ≥ 0.4 vs. H1: p < 0.4. A random sample of 1000 observations was taken from the population. Answer the following questions and show your Excel calculation for each question clearly: (a) Let p ̂ be the sample proportion. What is the standard error of sample proportion (i.e., σ_p ̂ ) if H0 is true? (b) If the sample proportion obtained were 0.38 (i.e., p ̂=0.38), what is its p-value?...
1. For a T distribution with 10 degrees of freedom, what is the probability P(T < -1.372)? 1. We consider a sample of 11 being used in a hypothesis test. In a two-sided hypothesis test where we reject if the value of |To| > Ta/2 is -2.05. Do you reject the null hypothesis in this case (explain why)? What is the p- value in this case (you may use a range for the p-value)? 2. This time a sample size...
The Student's t distribution table gives critical values for the Student's t distribution. Use an appropriate d.f. as the row header. For a right-tailed test, the column header is the value of α found in the one-tail area row. For a left-tailed test, the column header is the value of α found in the one-tail area row, but you must change the sign of the critical value t to −t. For a two-tailed test, the column header is the value...
4. It is desired to test H0 : µ = 20 Vs H1 : µ < 20, on the basis of a random sample of size 64 from normal distribution with population standard deviation σ = 2.4. The sample mean and sample standard deviation are found to be 19.5 and 2.5, respectively. (a) Test the hypothesis at α = 0.05. Compute the test statistics, critial regions, and perform the test. Will the result be difference if α is changed to...
Let x be a random variable that represents the pH of arterial plasma (i.e., acidity of the blood). For healthy adults, the mean of the x distribution is μ = 7.4.† A new drug for arthritis has been developed. However, it is thought that this drug may change blood pH. A random sample of 36 patients with arthritis took the drug for 3 months. Blood tests showed that x = 8.7 with sample standard deviation s = 3.4. Use a...
Let X be chi-squared with k = 5 degrees of freedom. (a) What is P[X > 1]? (This exact calculation requires some serious integration) (b) Find P[X > 1] with the normal approximation, i. e., approximate that probability assuming X ~ N(mu, sigma squared), where mu and sigma squared are the mean and variance of a Gamma(5/2, 1/2).
Unfortunately, arsenic occurs naturally in some ground water†. A mean arsenic level of μ = 8.0 parts per billion (ppb) is considered safe for agricultural use. A well in Texas is used to water cotton crops. This well is tested on a regular basis for arsenic. A random sample of 41 tests gave a sample mean of x = 6.9 ppb arsenic, with s = 2.7 ppb. Does this information indicate that the mean level of arsenic in this well...