If the inspection division of a county weights and measures department wants to estimate the mean amount of? soft-drink fill in? 2-liter bottles to within plus or minus0.02 liter with 95?% confidence and also assumes that the standard deviation is 0.09 ?liters, what sample size is? needed?
Solution :
Given that,
standard deviation = = 0.09
margin of error = E = 0.02
At 95% confidence level the z is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0.05 / 2 = 0.025
Z/2 = Z0.025 = 1.960
Sample size = n = ((Z/2 * ) / E)2
= ((1.960 * 0.09) / 0.02)2
= 77.79
Sample size = 78
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