HL Unit 9, Day 7: Descriptive Statistics
345
Table 9.12: Generating Cumulative Relative Frequencies at the Class Boundaries for a Frequency Distribution Class Class Class Cumulative Cumulative mark frequency boundary frequency relative frequency 57.5 0 0 59 3 60.5 0+3=3 3/50 = 0.06 62 10 63.5 3 + 10 = 13 13/50 = 0.26 65 20 66.5 13 + 20 = 33 33/50 = 0.66 68 12 69.5 45 45/50 = 0.90 71 5 72.5 50 50/50 = 1.00
Table 9.13: Cumulative Relative Frequency Table for Sample of Heights of Women at Gates College Class Cumulative boundary, x relative frequency, Fˆ (x) 57.5 0.00 60.5 0.06 63.5 0.26 66.5 0.66 69.5 0.90 72.5 1.00
(b) 30 < S â&#x2030;¤ 40.
[Ans: 136]
(b) Calculate an estimate for the mean salary, correct to 3 significant figures. [Ans: 24.7] (c) Note that we will find the median and quartiles in a way different than assuming all the values are at the class mark. Be aware that for continuous, grouped data, finding the median is not as easy as punching some buttons on the calculator.
Cumulative Frequency Polygon Once you have the cumulative frequency distribution, it is a simple matter to create the cumulative frequency polygon. Plot the class boundaries vs. the Mr. Budd, compiled September 29, 2010