Question

How many adults must be randomly selected to estimate the mean FICO​ (credit rating) score of working adults in a​ country? We want ​% confidence that the sample mean is within points of the population​ mean, and the population standard deviation is .

Answer 1

Answer: hello below is the complete question

How many adults must be randomly selected to estimate the mean FICO (credit rating) score of working adults in a country? We want 90% confidence that the sample mean is within 4 points of the population mean, and the population standard deviation is 66. Round up to the nearest whole number

answer : 737 adults

Step-by-step explanation:

confidence interval = 90% = 0.9

( E ) = 4

standard deviation = 66

first we have to calculate the value of a

a = 1 - confidence interval

  = 1 - 0.9 = 0.10      hence  a / 2 = 0.05

next find the value of Z a/2 from table

Z$_{0.05}$  = 1.645

The number of Adults selected can be determined using this relation

N = $(Z_{a/2} * (s/E))^2$

   = $(Z_{0.05} * ( 66/4))^2$

   = 737