Suppose you calculate a 95% confidence interval for the population mean (population variance is not known) to be [5.31, 6.22], using sample data of size 40. Which of the following are true: O the sample variance in this case is 0.235. It is possible to increase the confidence level by trading off precision (i.e. a wider resulting CI) () if we were to use sample data coming from a larger random sample of size 50, we would definitely get a narrower confidence interval. (Note: we don't have information about the population variance). It is possible to reduce the width of the confidence interval by increasing the cconfidence level. the sample mean in this case is 5.765