solution: First, we compute the mid-value of class interval denotes by X. Mid-value is the sum of upper and lower class boundary divided by 2. (50 + 59)/2 = 54.5 X f Xf 54.5 13 708.5 64.5 6 387 74.5 7 521.5 84.5 7 591.5 94.5 7 661.5 Sum = 40 2870 Mean = ∑fX/∑f Mean = 2870/40 Mean = 71.75 Solution: 30 35 43 44 47 48 54 55 56 57 59 62 63 65 66 68 69 69 71 72
