the imo transport company, in order to further enhance its performance is trying to decide whether to purchase brand a or brand b tires for it fleet of vehicle. in order to estimate the difference in the 2 brands. an experiment was conducted using a random sample of 20 tires off brandy and 18 tires of brand b. the result shows that for brand a; X¹=30,500km, S¹=45,000km and for Brand b; X²=27,880km, S²= 3750km. compute a 90% confidence limit for u¹-u², assuming the population to be normally distributed

Martha has a deck of cards. she has lost some of the cards, and now the deck only contains nine spades, eleven diamonds, eight clubs, and twelve hearts. martha predicts that whenever she draws a card from the deck without looking, she will draw a club one-fifth of the time. which activity would best allow martha to test her prediction? a. randomly draw a card from the box and see if it is a club. b. randomly draw a card. then, continue to draw another card until all eight clubs are drawn. c. randomly draw and replace a card 120 times. then, observe how close to 30 times a club is drawn. d. randomly draw and replace a card 100 times. then, observe how close to 20 times a club is drawn.