5a. 依題要用到standard normal distribution既table , 例如
https://freakonometrics.hypotheses.org/9404
ai) 俾左兩個數字你,實係計番佢個standard score
(174.5 - 181) / 13 = -0.5
(200.5 - 181) / 13 = 1.5
之後睇番表,0.5果個數字係0.6915 , 對稱咁諗 -0.5 果個數字應該就係 1 - 0.6915 = 0.3085
所以有30.85%既人係小過 standard score -0.5 既
再到1.5,表果個數字係0.9332,即係93.32%既人係小過 standard score 1.5 既
即係 1 - 93.32% = 6.68% 既人係高過1.5既
所以最後既 probability = 30.85% + 6.68% = 0.3753
PS. 你要小心你果個表係米同條link個表一樣咁睇,唔同表既睇法有d分別
5b. 72 percentile即係0.72,你要搵表入面既0.72應該會搵到最近係0.58
但係0.58係standard score => (? - 181) / 13 = 0.58 => ? = 188.54
我就咁睇表correct唔到4 d.p.
但係個idea都係咁
如果佢俾左個分 , 一般就計standard score再睇表搵probability
如果佢俾左個probability (eg. percentile),一般就睇表入面搵番standard score 再計番個數