For a 4-unit class like Statistics, students should spend average of 12 hours studying for the class. A survey was done on 24 students, and the distribution of total study hours per week is bell-shaped with a mean of 13 hours and a standard deviation of 2.8 hours. Use the Empirical Rule to answer the following questions. a) 68% of the students spend between hours and hours on Statistics each week. b) 95% of the students spend between hours and hours on Statistics each week. c) 99.7% of the students spend between hours and hours on Statistics each week.
Answer:
Given,
mean = 12
standard deviation = 2.8
n = 24
a)
By using Empirical rule, 68% of the Students spend between
consider,
xbar +/- z*sigma/sqrt(n)
substitute values
= 12 +/- 1*2.8/sqrt(24)
= 12 - 0.572 , 12 + 0.572
= (11.428 , 12.572)
So 68% of the Students spend between 11.428 hours and 12.572 hours on Statistics each week.
b) Now 95% of the students spends
xbar +/- z*sigma/sqrt(n)
substitute values
12 +/- 2*2.8/sqrt(24)
= 12 +/- 1.143
= 12 - 1.143 , 12 + 1.143
= (10.857 , 13.143)
So 95% of the Students spend between 10.857 hours and 13.143 hours on Statistics each week.
c) 99.7% of the Students spend
xbar +/- z*sigma/sqrt(n)
substitute values
12 +/- 3*2.8/sqrt(24)
= 12 +/- 1.715
= 12 - 1.715 , 12 + 1.715
= (10.285 , 13.715)
99.7% of the Students spend between 10.285 hours and 13.715 hours
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