Quiz 1: Freedman, et al., Chapter 3 Name lon Frous PSYC 1303 Statistical Methods
ID: 3070243 • Letter: Q
Question
Quiz 1: Freedman, et al., Chapter 3 Name lon Frous PSYC 1303 Statistical Methods -Version 1. In a Public Health study, a histogram was plotted showing the number of cigarettes per day smoked by each subject (current smokers). The histogram appears to the right. The density is marked in parentheses. The class intervals include the right endpoint, not the left. There are 2Ocigarettes in a pack. 4 (3.5) 02 (1.5) 1.5) Co.5) 40 Number of cigarettes o 10 20 0 Circle the correct answer to the following questions: (2 points each) (a) The percent who smoked exactly 50 cigarettes per day is around... (0.59) t 15% 5% 3.5% 1.5% (b) The percent who smoked more than a pack a day is around. 12 41.5 (15%)/ 1.5% 80% 50% 35% (c) The percentage who smoked 20 cigarettes or less per day is around. 0) 1.5% 2-20% 80% 15% (d) The percentage who smoked at least half a pack of cigarettes, but not more than 2 packs,is around. 85% 65% 35% 15% 0.5%Explanation / Answer
Since the densities are mentioned in the histogram, let us first find the frequency of each class.
Frequency of a class= Class width*density
Class Freq Relative frequency
0-10 15 0.15
10-20 35 0.35
20-40 30 0.30
40-80 20 0.20
Relative freq of a class= Freq of that class/ Total frequency, here total frequency =100
a) 0.5%(already correct)
b) The percent who smoke more than a pack a day = sum of relative frequencies of classes 20-40 and 40-80 =0.3+0.2 = 0.5 or 50%(Ans)
c) 50% (already correct)
d) The percentage who smoked atleast half a pack of cigarettes, but not more than 2 packs = sum of relative frequencies of classes 10-20 and 20-40 = 0.35+0.30 =0.65 or 65% (Ans)
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