155
Exercise 10.12
The average number of English courses taken in a two–year time period by male and female col-
lege students is believed to be about the same. An experiment is conducted and data are collected
from 29 males and 16 females. The males took an average of 3 English courses with a standard
deviation of 0.8. The females took an average of 4 English courses with a standard deviation of
1.0. Are the averages statistically the same?
Exercise 10.13
(Solution on p. 166.)
A study is done to determine if students in the California state university system take longer to
graduate than students enrolled in private universities. 100 students from both the California state
university system and private universities are surveyed. Suppose that from years of research, it
is known that the population standard deviations are 1.5811 years and 1 year, respectively. The
following data are collected. The California state university system students took on average 4.5
years with a standard deviation of 0.8. The private university students took on average 4.1 years
with a standard deviation of 0.3.
Exercise 10.14
A new SAT study course is tested on 12 individuals. Pre-course and post-course scores are
recorded. Of interest is the average increase in SAT scores. The following data is collected:
Pre-course score
Post-course score
1200
1300
960
920
1010
1100
840
880
1100
1070
1250
1320
860
860
1330
1370
790
770
990
1040
1110
1200
740
850
Table 10.1
Exercise 10.15
(Solution on p. 166.)
A recent drug survey showed an increase in use of drugs and alcohol among local high school
seniors as compared to the national percent. Suppose that a survey of 100 local seniors and 100
national seniors is conducted to see if the percentage of drug and alcohol use is higher locally than
nationally. Locally, 65 seniors reported using drugs or alcohol within the past month, while 60

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