A pediatrician is conducting an experiment to determine which brand of baby food (A, B, or C) and amount of tummy time (half an hour a day or none) will produce healthier babies, determined by weight gain in the first few months
after starting the baby food. Her patients are divided into equally sized groups and are randomly assigned to a
brand of baby food and amount of tummy time. In this experiment the subjects were randomly assigned to the
different treatments. What is the most important reason for this random assignment?
FA!
O Random assignment reduces the amount of variation in baby weights.
O Random assignment makes it possible to make a conclusion about all babies.
O Random assignment prevents the placebo effect from ruining the results of the study.
O Random assignment eliminates the effects of other variables such as parental involvement and socioeconomic
class
O Random assignment is a good way to create groups of subjects that are roughly equivalent at the beginning of the
experiment

(20 points) a bank has been receiving complaints from real estate agents that their customers have been waiting too long for mortgage confirmations. the bank prides itself on its mortgage application process and decides to investigate the claims. the bank manager takes a random sample of 20 customers whose mortgage applications have been processed in the last 6 months and finds the following wait times (in days): 5, 7, 22, 4, 12, 9, 9, 14, 3, 6, 5, 15, 10, 17, 12, 10, 9, 4, 10, 13 assume that the random variable x measures the number of days a customer waits for mortgage processing at this bank, and assume that x is normally distributed. 2a. find the sample mean of this data (x ě…). 2b. find the sample variance of x. find the variance of x ě…. for (c), (d), and (e), use the appropriate t-distribution 2c. find the 90% confidence interval for the population mean (îľ). 2d. test the hypothesis that îľ is equal to 7 at the 95% confidence level. (should you do a one-tailed or two-tailed test here? ) 2e. what is the approximate p-value of this hypothesis?