Question

12. Using a normal distribution and z score formula answer the following questions: a. Find the Z-score that cuts off the top 35% of the nornval curve b. Find the data value to the nearest whole number that cuts off the bottom 20% of the curve given that the mean is 75 and sample standard deviation is 5. c. Find the z scores that cut off the middle 50% of the normal curve. 13. This question is worth 4 points only. A statistics professor has surveyed 225 NCC students to determine the cost of their textbooks for the semester. He determined that the sample mean was $425 with a population standard deviation of $75 i) ii) iii) Determine the standard error of a 95% confidence interval Determine the 95% confidence interval (round to the nearest whole number) Determine the 99% confidence interval (round to the nearerst whole #f)

12 and 13

Answer 1

a 1-035 =o15 } = o-S) = 639 26 6 5 9-05 5 리 A 1 - 0 20 - 0-30 (2P =o-30) = -0.53 5 Ta 7235 DO5o l= 025) -5067 O

(13) رہا = 7 2 2 - (2 ر2 S.E- & 25 (5) (2) 2 0 = م - 28/ / 26 مرج از Th (2+ 7.46 25 152) کی 2 + 25 - 3 , (. ک/ م /1 ريدر 4/3) 77 ي= -- / 2 کی 2 رل) 22 + کا + کا کی :2 ا 33 ,2 // |