Q1: Suppose that Y, Y2, , Y constitute a random sample from a normal distribution with known mean u and unknown variance a. The most powerful a-level test is sued for testing Ho:g = og versus HA:02 o, where af > af. نقطة واحدة .3 3. The rejection region is given by RR = {E".. ("")*SK}

2. Suppose it is claimed that amongst the population of STM1001 students, the number of items bought online in the past year is normally distributed with a mean of u 20 and variance of o2 = 25. Further suppose that we wish to study the mean of the population by taking a random sample of n = 61 STM1001 students. Using this information, write down the distribution of the sample mean, X. Note: In each box, enter a single number rounded to four decimal places where relevant. (2 marks) X~ N( 20 0.4098 2 4. Again following on from the previous question, what is the probability that when we take a random sample of n = 61 STM1001 students, the sample mean would be either greater than 20.3521 or less than 19.6479? [int. orty will b own that

Assume that the height of male students in a large university is normally distributed with mean 172.7 cm and variance 57.76 cm². (a) Suppose 80 random samples, each with 25 male students are obtained. In how many samples would you expect the sample mean to be between 169.66 cm and 173.46 cm? Give you answer to one decimal place. Answer: number of samples = (b) Suppose 6 random samples, each with 25 male students are obtained. Compute the probability that exactly 4 of the 6 samples will have its sample mean between 169.66 cm and 173.46 cm. Give your answer to two decimal places. Answer: probability=

4. Researchers working for a sports drink company would like to know if a new blend if its popular sports drink can help improve marathon runners' final running time. Marathon times, Y, are known to follow a Normal distribution. Suppose that runners using the old blend sports drink have a mean finishing time of 300 minutes (µ = 300 minutes). A random sample of 20 runners was selected to use the new blend of sports drink in a marathon, finishing with an average time of 270 minutes and a standard deviation of 20 minutes (y = 270 min, s = 20 min). Can it be claimed that the new blend lowers finishing times? COr is it possible that random chance alone can explain the discrepancy? Carry out a hypothesis test of the true mean u using the 4- step procedure. Set your alpha-level to 0.05. %3D c. Which test statistic and sampling distribution under the null should we use? O i. z-score; standard Normal O ii. t-statistic; Student'st