Parents of teenage boys often complain that auto insurance costs more, on average, for teenage boys than for teenage girls. a group of concerned parents examines a random sample of insurance bills. sample 1 is comprised of 31 teenage boys sample 2 is comprised of 26 teenage girls. the mean annual cost for teenage boys was 725. for teenage girls, it was 600. from past years, it is known that the population standard deviation for boys is 180 and for girls is 185. determine whether or not you believe that the mean cost for auto insurance for teenage boys is different than that of teenage girls, using α=0.05.

Rate of return, standard deviation, coefficient of variation personal finance problem mike is searching for a stock to include in his current stock portfolio. he is interested in hi-tech inc.; he has been impressed with the company's computer products and believes hi-tech is an innovative market player. however, mike realizes that any time you consider a technology stock, risk is a major concern. the rule he follows is to include only securities with a coefficient of variation of returns below 1.07. mike has obtained the following price information for the period 2015 through 2018:hi-tech stock, being growth-oriented, did not pay any dividends during these 4 years. a. calculate the rate of return for each year, 2015 through 2018, for hi-tech stock. b. assume that each year's return is equally probable and calculate the average return over this time period. c. calculate the standard deviation of returns over the past 4 years. (hint: treat this data as a sample.) d. based on b and c determine the coefficient of variation of returns for the security. e. given the calculation in d what should be mike's decision regarding the inclusion of hi-tech stock in his portfolio?