Solution :
Given that,
standard deviation = =45.1
Margin of error = E = 2.5
At 98% confidence level the z is ,
= 1 - 98% = 1 - 0.98 = 0.02
/ 2 = 0.02/ 2 = 0.01
Z/2 = Z0.01 = 2.326 ( Using z table )
sample size = n = [Z/2* / E] 2
n = ( 2.326*45.1 / 2.5 )2
n =1760.72
Sample size = n =1761
( when you have z value 2 decimal Z0.01 = 2.33 when n=1766.78=1767)
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