How old was Sarah x years ago if she is now 23?
2 answers:
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Answer:
The 90 % confidence interval for the mean population is (11.176 ; 20.824 )
Rounding to at least two decimal places would give 11.18 , 20.83
Step-by-step explanation:
Mean = x`= 16 miles per hour
standard deviation =s= 4.1 miles per hour
n= 4
= 4.1/√4= 4.1/2= 2.05
1-α= 0.9
degrees of freedom =n-1= df= 3
∈ ( estimator t with 90 % and df= 3 from t - table ) 2.353
Using Students' t - test
x`±∈ *
Putting values
16 ± 2.353 * 2.05
= 16 + 4.82365
20.824 ; 11.176
The 90 % confidence interval for the mean population is (11.176 ; 20.824 )
Rounding to at least two decimal places would give 11.18 , 20.83