only C and D

W=6

A researcher wants to find out the true mean weight (in kg) of kindergarten students in DEF country. Based on previous study, the distribution of weight of kindergarten students in DEF country is approximately normal. A pilot study is conducted and 10 kindergarten students in DEF country are randomly selected. Their weights are listed as below. 13.2 14.1 12.5 14.6 18.9 19.5 15.4 16.6 18.2 21.1 (a) Find the mean and standard deviation of weights of the above 10 sample data. Correct the final answers to 2 decimal places. (b) The researcher claims that the true mean weight of kindergarten students in DEF country is not equal to 17.5kg. Perform a hypothesis testing using critical value approach to test the researcher's claim at 1% significance level. Correct the test statistic to 2 decimal places. (c) Construct a 98% confidence interval for the true mean weight of kindergarten students in DEF country. Correct the final answers to 1 decimal place. (d) Given that the population standard deviation is known to be (3.8+0.1xW) kg. How many additional samples are required if the researcher wants to estimate the true mean weight of kindergarten students in DEF country within 0.6kg with 99% confidence