Question

If 36 randomly selected candy boxes recorded a mean weight of 23 lbs. Assume that the standard deviation of these candy boxes is 6.7 lbs. Construct 90% confidence intervals of true mean weight of candy boxes and comment about it.

Answer 1

Solution :

Given that,

Point estimate = sample mean = = 23

Population standard deviation =    = 6.7
Sample size = n =36

At 90% confidence level

= 1 - 90%  

= 1 - 0.90 =0.10

/2 = 0.05

Z/2 = Z0.05 = 1.645

Margin of error = E = Z/2    * ( /n)

= 1.645 * ( 6.7/  36 )

= 1.84
At 90% confidence interval
is,

- E < < + E

23 - 1.84 <   < 23 + 1.84

21.16 <   < 24.84