In: Statistics and Probability
Here, = 481/700 = 0.6871
a) In general, (1-)%
confidence interval for the population proportion is obtained as
follows :
where Z (/2)
= Z (0.05) = 1.6449
Thus, 90% confidence interval for the population proportion
is:
( 0.6583 , 0.7159 )
( 460.81, 501.149 ) (Here n = 700 is multiplied to the above 90%
CI )
b) Since the 90% confidence interval for the population proportion does not contains values less than 450, it would be unusual if less than 450 students indicated that they have read a book for personal enjoyment during the school year.
c) 99% confidence interval for the population
proportion is:
( 0.6420, 0.7322 )
( 449.400, 512.540 ) (Here n = 700 is multiplied to the above 90%
CI )
Since the 99% confidence interval for the population proportion
does contains values less than 450, it would not be unusual if less
than 450 students indicated that they have read a book for personal
enjoyment during the school year.
Hope this answers your query!