d with finding a 95% confidence interval for a population mean. You do not know the standard deviation of the population, nor do you know its distribution. Your sample size is 23, and you have found the sample mean and sample standard deviation. Which of the following equations for the interval estimate endpoints should you use to find the confidence interval?

Dianne has a choice of two routes to drive to work. She timed her journey along each route on several occasions and the times in minutes are given below:Town route: 15, 16, 20, 28, 21Country route: 19, 21, 20, 22, 18(i) Calculate the mean and standard deviation (to one d. p.) of each set of journey times.(ii) Which route would you recommend? Give a reason.

There are two national college-entrance examinations, the scholastic aptitude test (SAT) and the American College Testing program (ACT).  Scores on the SATs are approximately normal with mean 500 and standard deviation 100.  Scores on the ACTs are approximately normal with mean 18 and standard deviation 6. Use the links provided for the Normal  (Links to an external site.)calculator and the Inverse Normal  (Links to an external site.) calculator to help complete the problems, you do not need to do any work out by hand. (instructions on how to use these calculators can be found in the week 5 star on the home page)  a)  What percent of all SAT scores are above 600? b)  Which is the greater accomplishment, scoring 630 on the SAT or 22 on the ACT ? Explain your reasoning for your choice. c)  How high a score in the SAT is needed to place in the top 2.5%.

You determine that the standard deviation for a sample of test scores is 0.  This tells you that 1 all the test scores must be 0. 2 all the test scores must be the same value. 3 there is no straight-line association. 4 the mean test score must also be 0. 5 you made a mistake because the standard deviation can never be 0.