-4. Suppose that samples of size n= 25 are selected at ran- dom from a normal population with mean(100)and standard deviation 10. What is the probability that the sample mean falls in the interval from u-1.7o to u, +1.50 , ? X

5. Suppose the time spent by a randomly selected student at a campus computer laboratory has a gamma distribution with mean 20 min and variance 80 min². (a) What are the values of a and B? (b) What is the probability that a student spends between 20 and 40 min at the laboratory? (c) Only 1% of students will spend more than how many minutes at the laboratory?

5. Suppose X is the number of successes in a random sample of size n from a large population with a proportion of success p. What are the mean and the standard deviation of the sampling distribution of X in terms of n and p? The mean is p(l-pland the standard deviation is p(1-p) b. The mean is npand the standard deviation is ap(1-p). The mean is p(1-pland the standard deviation is pp. C. d. The mcan is 7pand the standard deviation is rp.

4. Let X be a random variable representing dividend yield of Australian bank stocks. We may assume that X has a normal distribution with standard deviation = 2.4%. A random sample of 19 Australian bank stocks has a sample mean of = 8.71%. For the entire Australian stock market, the mean dividend yield is = 5.9%. Do these data indicate that the dividend yield of all Australian bank stocks is higher than 5.9% ? Use Q=.05. Are the data statistically significant at the given level of significance? Based on your answers, will you reject or fail to reject the null hypothesis? A. The p-value is less than the level of significance and so the data are not statistically significant. Thus, we reject the null hypothesis. B. The p-value is less than the level of significance and so the data are statistically significant. Thus, we fail to reject the null hypothesis. C. The p-value is greater than the level of significance and so the data are statistically significant. Thus, we fail to reject the…

If a random member (x) is selected from a normal distribution having a mean of 80 and standard deviation of 5, what is the probability that the value of x lies between 78 and 83? Show your formula etc along with your answer.

5. Let x be a random variable that represents the level of glucose in the blood (milligrams per deciliter of blood) after a 12-hour fast. Assume that for people under 50 years old, x has a distribution that is approximately normal, with mean u = 85 and estimated standard deviation a = 25. A test result x< 40 is an indication of severe excess insulin, and medication is usually prescribed. (a) What is the probability that, on a single test, x < 40? That's find P(x < 40) (b) Suppose a doctor uses the average x fot two tests taken about a week apart. What is the probabilit that ( Hint: Your standard deviation here should be ) P(ĩ < 40)

5. The distribution of heights of a certain breed of terrier has a mean of 72 centimeters and a standard deviation of 10 centimeters, whereas the distribution of heights of a certain breed of poodle has a mcan of 28 centimeters with a standard deviation of 5 centimcters. Assume the distributions of both types of breeds are normally distributed. (n) Suppose we are taking a random sample of 64 terriers. What is the sampling distri- bution of mean heights of the breed of terriers? (b) Find the probability that the sample mean for a random sample of heights of 61 terriers excoedls 75 centimetcrs. (c) Find the probability that the sample mean for a random sample of heights of 64 terriers excoeds the sample mean for a random sample of heights of 100 poodles by at lenst 44.2 centimeters.

13.36 (EX) Pregnancy lengths 1/2: The length of human pregnancies from conception to birth varies according to a distribution that is approximately Normal with mean 266 days and standard deviation 16 days. A study enrolls a random sample of 16 pregnant women. The mean of the sampling distribution of is 266 ¡X is The standard deviation of the sampling distribution of 4 (No decimal) (No decimal)

7. For each of the following samples that were given an experimental treatment,test whether they represent populations that score significantly higher thanthe general population: (a) a sample of 100 with a mean of 82, (b) a sample of10 with a mean of 84. The general population of individuals has a mean of 81,a standard deviation of 8, and follows a normal curve. For each sample, carryout a Z test using the five steps of hypothesis testing with a one-tailed test atthe .01 significance level, and make a drawing of the distributions involved.(c) ADVANCED TOPIC: Figure the 99% confidence interval for parts (a)and (b).